EX  LIBRIS 

BARNES  WOODHALL 


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Z O O N O M I As 


the  laws 

O F 


ORGANIC  LIFE. 


ZOONOMIAs  . 


O R 


THE  LAWS 

O F 

ORGANIC  LIFE. 


VOL.  I, 


By  ERASMUS  DARWIN,  M.  D.  F.  R.  S. 

AUTHOR  OF  THE  BOTANIC  GARDEN. 


Principid  coelum,  ac  terras,  camposque  liquentes, 
Lucentemque  globum  lunae,  titaniaque  astra, 

Spiritus  intus  alit,  totamque  infusa  perartus 
Mens  agitat  molem,  et  magno  se  corpore  miscet. 

Virg.  JE n.  vi. 

Earth,  on  whose  lap  a thousand  nations  tread, 

And  Ocean,  brooding  his  prolific  bed, 

Night’s  changeful  orb,  blue  pole,  and  silvery  zones, 
Where  other  worlds  encircle  other  suns, 

One  Mind  inhabits,  one  diffusive  Soul 

Wields  the  large  limbs,  and  mingles  with  the  whole. 


NE  TV-  YORK: 

Printed  by  T.  & J.  SWORDS,  Printers  to  the  Faculty  of  Phylic  of 
Columbia  College,  No.  99  Pearl-Street. 


. JlW 


K 1 ** 


r-U)  > r-i 


m 


4 ’ ' 


•• 


DEDICATION. 


To  the  candid  and  ingenious  Members  of  the 
College  of  Phyficians,  of  the  Royal  Philofophi- 
cal  Society,  of  the  two  Univeriities,  and  to  all 
thofe  who  ftudy  the  Operations  of  the  Mind  as 
a Science,  or  who  pradlife  Medicine  as  a Pro- 
feffion,  the  fubfequent  Work  is, 

With  great  refpedl, 

Infcribed  by 

THE  AUTHOR. 

Derby,  May  i,  1794. 


CONTENTS 


Sect.  I. 
II. 

III. 

IV. 

V. 

VL 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

XIII. 

XIV. 
XV. 

XVI. 

XVII. 

XVIII. 

XIX. 

XX. 

XXL 

XXII. 

XXIII. 

XXIV. 


PREFACE  to  the  American  Edition. 

Lines  to  Erafmus  Darwin. 

Author’ s Preface. 

Of  Motion. 

Explanations  and  Definitions. 

The  AAotions  of  the  Retina  demonf  rated  by 
Experiments. 

Laws  of  Animal  Caufation. 

Of  the  four  Faculties  or  Motions  of  the  Sen- 
forium. 

OJ  the  four  Clajfes  of  Fibrous  AAotions. 

Of  Irritative  AAotions. 

Of  Scnftive  AAotions. 

Of  F oluntary  AAotions. 

Of  Affociate  AAotions. 

Additional  Obfcrvations  on  the  Senforial 
Powers. 

Of  Stimulus , Senforial  Exertion,  and  Fibrous 
Contraction. 

Of  F egetable  Animation. 

Of  the  Production  of  Ideas. 

Of  the  Clafjes  of  Ideas. 

Of  InJlinCt. 

The  Catenation  of  Animal  AAotions. 

Of  Sleep. 

Of  Reverie. 

Of  Fertigo. 

Of  Drunkennefs. 

Of  Propcnfity  to  AAotion.  Repetition,  Imi- 
tation. 

Of  the  Circulatory  Syfem. 

Of  the  Secretion  of  Saliva,  and  ef  Tears. 
And  f the  Lacrymal  Sack. 


Sect. 


CONTENTS. 


Sect.  XXV. 
XXVI. 

XXVII. 

XXVIII. 

XXIX. 

XXX. 

XXXI. 

XXXII. 

XXXIII. 

XXXIV. 

XXXV. 

XXXVI. 

XXXVII. 

. XXXVIII. 

XXXIX. 

XL. 


Of  the  Stomach  and  Intejiines. 

Of  the  Capillary  Glands , and  of  the  Mem- 
branes. 

Of  Haemorrhages. 

The  Paralyfes  of  the  Laffeals. 

The  Retrograde  Motions  of  the  Abforbent 
V tffels. 

The  Paralyfs  of  the  Liver. 

Of  Temperaments. 

Difeafes  of  Irritation. 

• of  Senfation. 

of  V olition. 

of  Affociation. 

The  Periods  of  Difeafes. 

Of  Digeflion,  Secretion , Nutrition. 

Of  the  Oxygenation  of  the  Blood  in  the 
Lungs  and  Placenta. 

Of  Generation. 

Of  Ocular  Speflra. 


PREFACE 


PREFACE 

TO  THE 

AMERICAN  EDITION. 


In  the  progrefs  of  cbfervaticn  and  experiment  in 
phyfics,  within  a few  years,  fuch  a number  of  new  and 
important  facts  have  been  brought  to  light,  that 
many  philofophers  have  believed  the  people  of  the  pre- 
fent  day  were  polTefred  of  a great  deal  more  know- 
ledge than  the  moderns  of  the  three  laid  centuries,  or 
their  ancient  predeceffors. 

This  opinion,  in  particular,  has  been  deemed  well 
founded,  and  true  in  its  refpedt  to  medicine,  which,  at 
this  time,  is  not  only  confidered  fufceptihle  of  new  ex- 
pofitions  and  interpretations,  but  of  being  greatly  im- 
proved and  enlarged,  both  in  theory  and  practice. 
And  although  among  thofe  who  think  thus  are  reck- 
oned molt  of  the  original  and  clear-lighted  geniufes  of 
cur  time,  yet  there  are  not  wanting  fome,  and  thofe 
men  of  talents  and  reputation  too,  who  are  in  the  ha- 
bit of  thinking,  if  the  ancients  knew  not  quite  as  much 
as  ourfelves,  yet  their  writings  contain  the  leading 
hints,  or  great  outlines  of  almofc  every  thing  difcover- 
able,  either  diredtly  expreued,  or  fignified  in  allegori- 
cal terms.  This  literary  fuperftition  'has  been  carried  a 
great  way ; and  if  it  had  flopped  at  declaring  the  Iliad 
the  bell  of  poffible  poems,  or  the  Philiipics  the  moft 
finished  of  the  rhetorical  productions,  I fhouldnot  at  this 
time  have  troubled  myfelf  to  contradict  it.  But  when 
thefe  enthufiafsic  admirers  of  antiquity  declare,  that, 
in  matters  of  lcience  as  well  as  of  letters,  the  fubjedts  of 
enquiry  have  been  exhaufted  two  thoufand  years  ago, 

a and 


X 


PREFACE  TO  THE 


and  that  no  idea  can  be  Farted  which  is  not  an  imita-* 
tion  of  fomething  that  a Greek  or  a Roman,  or  fome 
body  elfe,  had  thought  before,  I own  I am  a little  dif- 
pofed  to  believe  their  alfertions  are  grounded  neither 
in  truth  nor  in  the  nature  of  things.  For  why  muft  we 
refort  to  the  Platonists,  Stoics,  and  Peripate- 
tics, for  doctrines  which  the  A c a d e m y , the  P o r c h,  . 
and  the  Lyceum  never  knew? 

Thefe  remarks  are  made  in  confer uence  of  an  opi- 
nion propagated  and  believed  by  fome,  that  a certain 
method  of  reafoning  upon  medical  lubjbts,  and  of 
p raft i ling  phytic,  introduced  now  of  late,  as  many  be- 
lieve, which  is  already  pretty  well  efLbiifhed,  and  ac- 
quiring rapidly  more  and  more  adherents,  is  in  fact  but 
a revival  and  new-modelling  of  the  opinions  and  pro- 
cedure of  the  Methodic  Sect,  founded  by  Ascle- 
Piades,  the  cotemporary  of  Mithridates  and 
Crassus. 

In  order  to  know  whether  this  opinion  is  wrell  found- 
ed, I fnall  enquire  what  the  philo fophy  of  the  Metho- 
dic Sect  was. 

Its  founder,  Asclepiades,  adopted  that  philofo- 
Pb-y>  whofe  foundation  had  been  laid  by  Anaxago- 
ras, Empedocles,  and  Heraclitus,  and  which 
was  afterwards  wrought  up  into  the  Atomic  Syjiem,  by 
Leucippus,  and  Democritus,  of  the  Eieatic  Sect, 
who,  rejecting  ail  metaphyhcal  explanations  of  the 
caufes  of  things,  undertook  the  interpreting  nature, 
from  the  laws  of  matter  and  motion.  This  was  af- 
terwards commented  upon,  enlarged,  and  adorned  by 
Epicurus,  lb  as  to  form,  what  was  afterwards  called 
the  Epicurean  PhilofopJiy.  What  the  details  of  this 
are,  may  be  leen  in  Diogenes  Laertius,  in 
Brucker,  and  his  tramlator  En  f i e l d,  as  well  as  in  the 
poem  of  Lucretius,  who  has  confeifedly  attempted 
a poetical  display  of  thefe  very  doctrines.  A general 
view,  comp  riling  a mere  lkctch  of  the  fyftem  of  this 
Ay]ojjio#j£jo;  as  far  as  connected  with  the  prefent  fubject, 

is 


AMERICAN  EDITION. 


XI 

is  all  I fhall  offer  here.  An  Epicurean  would  explain 
himfelf  thus: — £C  It  is  clear,  from  the  changes  which 
natural  bodies  undergo,  that  there  is  a perpetual  for- 
mation and  deftruction  of  them  going  on ; there  muft 
then  exift  matter  of  which  thefe  things  are  formed, 
-and  into  which  .they  are  refolved ; and  hence  proceeds 
the  conclufion  which  is  the  ground-work  of  the  fyftsm, 
that  a thins  can  neither  be  made  out  of  nothin?,  nor 
reduced  to  nothing.  ‘ Nullam  r.em  e nihilo  gigni  divi- 
nitus  unquam The  .univerfe,  therefore,  as  to  its  con- 
ftituent  atoms  or  particles,  was  always  as  it  is  at  pre.- 
fent  j and  confequently  matter  is  eternal.  The  work- 
man cannot  perform  any  thing  without  materials ; and 
thefe  felf-exiftent  materials,  in. the  decay  and  renova- 
tion they  undergo,  account  for  .the  phenomena  of  na- 
ture and  of  art.  If  things  were  created  out  of  nothing, 
then  every  kind  {liquid  proceed  from  each,  and  the 
greate'ft  irregularity  enfue;  men  fhould  be  produced 
in  the  lea,  fifties  on  the  land,  and  cattle  in  the  clouds ; 
generation  would  be  ufelefs,'  and  food  unneceftary : if 
they  returned  to  nothing,  then,  in  the  courfe  ofpaft  ages, 
through  wafte,  oonfumption,  and  lofs,  much  muft  have 
vanifhed  to  non-exiftence,  and  have  been  completely 
annihilated.  But  neither  of  thefe  fuppofitions  is  true, 
lince,  out  of  the  wreck  or  ruin  of  one  being;  or  exift- 
ence,  nature,  we  know,  without  an  aft  of  creation  or 
annihilation,  can  work  up  the  old  materials  into  a new 
fabric. 

“ All  exiftences  in  nature  are  referable  to  two  kinds, 
i . Bodies ; and,  2.  The  inane,  or  void  in  which  they  exift. 

“ Our  fenfes  fatisfy  us  of  the  exiftence  of  bodies,  as 
alfo  do  their  actions  paftions,  and  refitting  powers ; par- 
ticularly as  they  operate  upon  each  other,  and  upon 
our  touch : 

“ Tangere  enim  et  tang!  nisi  corpus  nulla  potest  res.” 

“ From  the  exiftence  and  motion  of  bodies  is  in- 
ferred the  exiftence  of  fpace ; and  the  effedt  of  bodies 
operating  upon  each  other  is  denominated  “ an  event  ■” 

and 


PREFACE  TO  THE 


xii 

and  if  there  was  not.  a void  there  would  not  be  a 
poflibility  of  motion ; for  if  a plenum  exifted,  then  every 
portion  of  fpace  being  clofety  impacted  and  wedged 
with  folidity,  the  moft  uniform  reft  and  dead  ftilliiefs 
would  pervade  the  whole  of  nature. 

“ As  to  bodies,  they  either  confift  of  elementary 
atoms,  or  of  fubftances  formed  from  thefe;  and  theie 
primordial  particles,  notvvith ftanding  foms  appearances 
to  the  contrary,  are  fimple,  iolid,  and  inaivifible. 

“ Sunt  igitur  solida,  ac  sine  inani  corpora  prinna.” 

“ All  thefe  atoms'  poffefs  the  fame  general  proper- 
ties, and  do  not  differ  from  each  other  in  arm  eftential 
refpeft.  Though,  from  their  different  operations  up- 
on the  fenfes,  is  inferred  a difference  among  them  as 
to  lize,  fftape,  and  heayinels.  Their  figures,  in  parti- 
cular, are  varied  in  an  endiefs  manner,  io  as  to  take  on 
every  mechanical  form;  but  in  all  thefe  cafes  they  are 
ftiil  infrangible  and  incapable  of  farther  diviiion. 

“ Each  atom  contains,  within  itfelf,  an  active  energy, 
or  internal  force,  by  which  it  is  either  conftantiy  in 
motion,  or  making  an  effort  to  move ; and  this  is  de- 
nominated gravity.  Thefe  atoms,  impelled  by  gravity 
through  void  fpace  in  curvilinear  courles,  it.' ike  again  ft 
each  other,  exercife  repelling  powers,  and  produce  vi- 
bration or  agitation ; and  as  this  gravitating  power  is 
eftential  to  matter,  it  can  never  be  inactive,  but  muft 
be  always  at  work.,  and  has  been  fo  from  eternity. 

“ Every  compound  body,  being  made  up  of  indivi- 
dual atoms,  therefore  poffeffes  the  united  energy  of  them 
all,  which  energy  is  the  foie  agent  in  nature;  but  by 
reafon  of  their  different  figures,  their  varied  magni- 
tudes, and  particular  fituations,  it  is  varioufly  modifi- 
ed ; as  when  the  atoms  are  hooked  or  rough,  motion 
will  be  retarded  among  them,  and  be  facilitated  when 
they  are  round  and  fmooth,  as  in  the  principles  of  fire 
and  animation.  Bodies  thus  being;  comooted  of  atoms, 
derive  their  adhons  from  the  energy  inherent  in  and 
proceeding  from  thefe  atoms. 


‘ Adi 


AMERICAN  EDITION. 


xiii 

“ All  alterations  happening  in  bodies,  whether  in 
their- fhape,  hardnefs,  iweetnefs,  &c.  are  afcribable  to 
the  change  taking  place  in  the  arrangement,  difpofi- 
tion,  &ct  of  the'  confiitnent  particles  ; and  thus  poro- 
hty,  transparency,  elafticity,  malleability,  &c._  are  to 
be  accounted  for  in  the  fame  way.  Gravity  being  an 
effential  property  of  matter,  all  corpufcules,  and  all 
bodies  formed  of  them,  muft  be  heavy. 

“ Thus,  horn  thefe  properties  of  bodies,  their  feve- 
ral  combinations  and  mechanical  operations,  arife  other 
more  complex  phenomena,  referable  however  to  the 
principle  of  motion,  fuch  as  the  heating  of  bodies  from 
the  influx  of  loft,  round  and  fmooth  particles ; the  cool  - 
ing  of  them  from  the  ingrefs  of  atoms  of  oppolite  and  ir- 
regular figures ; even  fenfaticns,  both  of  the  plealureable 
and  painful  kinds,  motion,  reft,  and  time  itfelf,  are  con- 
tingences  to  bodies.  In  lhort,  the  whole  phenomena  of 
the  production,  growth,  nutrition,  decline,  and  dif- 
folution  of  bodies,  is  to  be  afcribed  to  an  alteration  of 
arrangement  in  the  particles,  and  to  their  addition  or 
iftbft  raction. 

“ Minerals,  plants,  and  animals  were  thus  produced 
m the  beginning,  according  to  thefe  mechanical  laws  of 
matter  and  motion,  and  fo  was  the  world  they  comppfe 
and  inhabit.  They  continue  to  propagate  their  kinds 
in  regular  ways,  becaufe  nature  has  become  accuftcm- 
ed,  by  habit , to  produce  them  in  an  order  fo  uniform 
as  to  look  like  delign.  The  eye,  however,  was  not  made 
for  feeing,  nor  the  ear  fpr  hearings  but  having  been 
accidentally  formed  in  fuch  a way  as  to  anfwer  thefe 
pur'pofes,  the  fentient  principle  within,  which  is  co-ex- 
iftent  with  the  organization,  finding  them  fit  for  the 
purpofes  of  fight  and  hearing,  makes  ufe  of  them  ac- 
cordingly. 

“ Senfation,  proceeding  from  the  arrangement  and 
texture  of  particles,  is  to  be  aicribed  to  their  peculiar 
magnitude,  fnape,  combination,  &c.  fo  that  inftead  of 
being  an  original  property  of  matter,  it  is,  in  fadt,  only 

an 


XIV 


PREFACE  TO  THE 


an  occasional  quality.  Death  is  the  privation  of  fenfa- 
tion,  in  confequence  of  the  feparation  of  the  fentient 
principle  from  the  body : and  this  fentient  principle, 
when  a man  dies,  is  decompounded  into  its  Ample 
atoms,  lofes  its  fenfitive  powers,  and  goes  into  other 
forms  and  combinations.  The  foul,  in  this  refpect,  re- 
fembling  the  e)^e,  which  is  no  longer  capable  of  per- 
forming its  functions  than  the  connection  of  its  or- 
ganized texture  with  the  body  lafts.” 

What  Asclepiades  did,  was  to  apply  the  princi- 
ples of  the  Epicurean  Philofophy  to  medicine,  and  this 
he  did  with  much  ingenuity  and  acutenefs.  Building 
upon  that  hypothefis,  he  fuppofed  the  human  body 
compofed  of  Epicurus’  ultimate  atoms,  which,  by  their 
figure,  proximity,  and  arrangement,  enabled  it  to  per- 
form its  functions;  and  in  a particular  manner,  that 
health  con  fifed  in  the  fymmetry  and  permeability  of 
certain  paftages  through  the  firm  parts,  which  he  called 
pores  j and  the  doling  up,  or  obstruction  of  thefe,  confti- 
tuted  difeafe.  He  imagined  the  fluids  to  be  formed 
of  particles,  varying  in  figure  and  fize,  and  thus  making 
all  the  varieties  of  them,  from  the  thickeft  blood  to  the 
moft  attenuated  animal  fpirits.  And  when  thefe 
fluids  moved  freely  through  their  pores,  the  body  was 
found ; but  when  they  were  too  narrow,  fo  as  to  pro- 
duce ftagnations,  or  fo  oblique  as  not  to  be  readily 
paflable,  then  indifpofi tion  enlued. 

Such  were  the  leading  principles  of  Asclepiades, 
and  he  had  many  followers,  among  whom  Themison 
of  Laodicea  was  the  moft  eminent.  He  rejected 
moft  of  the  fubtle  and  laboured  reafonings  of  his  mafter, 
and,  declaring  fuch  minute  inveftigations  were  ufelels, 
affirmed,  without  defending  to  particulars,  and  bur- 
thening  himfelf  with  details,  a phyfician  need  only  make 
himfelf  acquainted  with  the  general  principles  of  dif- 
eafes.  Thefe,  he  faia,  all  belonged  to  two  clafles.  i. 
Thofe  proceeding  from  laxity  and,  2.  Such  as  were 
caufed  by  fcnciure.  All  that  was  neceflary  to  be  done, 

therefore, 


AMERICAN  EDITION. 


xv 


therefore,  was  to  afcertain  to  which  clafs  any  given 
difeafe  belonged ; and  then,  if  to  the  former,  to  pre- 
fcribe  afiringent ; if  to  the  latter,  relaxing  remedies. 

The  regular  and  fyftemaiic  plan  which  Themison 
and  his  numerous  followers  adopted  in  their  practice, 
differing  very  widely  from  the  conjectural  and  uncertain, 
mode  of  other  phyficians,  cauled  them  to  be  called 
Methodists  ; and  they  are  to  this  day  known  in  hif- 
toryby  the  name  of  the  Methodic  Sect.  While 
Themison  was  reflecting  upon  his  fyftem,  and  endea- 
vouring to  advance  it  to  maturity,  he  died,  and  the  un- 
finifhed  work  was  taken  up  and  completed  by  his  fol- 
lower Thessalus.  He  lived  in  the  time  of  N e r o ^ 
and  having  rejected,  as  frivolous,  all  the  opinions  of  his 
predeceflors,  he  declaimed,  with  vehemence  and  fury, 
againft  the  phyficians  of  all  ages,  and  offered  to  inftruCt 
a beginner  in  the  art  of  medicine  in  the  fhort  duration, 
of  fix  months.  He,  with  a degree  of  arrogance  and 
impudence,  of  which,  as  no  parallel  is  known  to  have 
exifted  in  ancient  times,  it  can  only  be  found  in  the 
hiftory  of  modem  quackeiy,  took  upon  himfelf  the 
appellation  of  or  the  conqueror  of  phyfi- 

cians. 

After  Thessalus  the  feCt  began  to  decline  and 
dwindle,  and  although  Soranus,  Julian,  and 
Moschion  retarded  for  a while  its  downfall,  yet  it 
was  totally  abforbed  and  loft  in  the  Galenic  Doctrines 
which  followed. 

Thus,  from  an  examination  of  the  Methodic  SyJlern , 
it  is  evident  the  explanation  of  every  thing  in  the  ani- 
mal economy  is  attempted  upon  principles  of  me- 
chanism only. 

The  firft  notice  of  any  thing  elfe  requifite  to  give 
life,  and  regulate  its  functions,  teems  to  have  occurred 
to  Hippocrates,  the  cotemporary  of  Democritus 
and  Leucippus.  The  TO  EVOffjLUy  of  thi-s  fagacious  ob- 
ferver,  as  the  interpretation  of  the  word  imports,  ob- 
vioufly  means  an  exciting  power  in  animals : and  the 

effeCts 


xvl  PREFACE  TO  THE 

effe&s  of  animation  refultirig  ffbrri  this,  imperfectly 
known,  and  badly  explained,  doubtiefs  give  rife,  ac- 
cording to  the  opinion  and  judgment  of  the  different 
writers,  to  the  Nature  of  Sydenham,*  the  Aura  Vi- 
tal is  of  Van  He l mo nt, -f  the  Vis  natures  Medicatrix 
of  G A u b i us,'.j;  the  Amnia  Medico,  of  Stahl  and 
Nichols,^  and  the  learned  and  curious  treatife,  enti- 
tled Imp'elum  Faciens , of  Kaauw  Boerhaave.J! 

And  here  it  is  worthy  of  remark,  that  from  Hip- 
pocrates to  Brown,  all  writers  entertain  the  opi- 
nion of  a principle  or  power  within,  exifting  as  the 
caufe  of  life,  as  appears  by  the  adtive  fignificaiion  of  all 
their  terms ; whereas  the  idea  of  the  Brunbnians  is,  that 
the  organized  animal  iolid  poifelTes  no  internal  energy, 
and  would  always  remain  inactive,  uhiefs  excited  by 
ftimuli  from  without ; they  therefore  fpeak  of  cue  vi- 
tal capacity  in  the  pajjive  voice,  as  fuiceptible  of  being 
acted  upon. 

Herman  Boerkaavs,  in  his  account  of  the  dif- 
eafes  of  a lax  and  of  a rigid  fibre,  feems  again  to  relapfe 
into  the  mechanical  confederation  of  thefe  things;  but 
Haller,  by  his  numerous  and  luminous  experiments 
on  fenfibility  and  irritability,  led  the  way  to  a right 
mode  of  purfuingand  underftanding  fuch  enquiries. 

The  attention  of  Hoffman  had  been  turned  to  the 
confideration  of  the  nervcus  fyftem,  as  influencing  dif- 
eafes,  more  particular  than  any  other  perfori ; and  from 
his  writings  were  probably  taken  the  hints  which  ter- 
minated in  Cullen’s  doftrine  of  Excitement  and  Col- 
lapse y in  his  Phyiiological  Tract  ;4f[  enlarged  afterwards, 

and 

* Opera  Passim. 

f Equidem  sciant  Splritum  esse  aliquem  illud  imjietum  faciens 
Mifipocrates , vitas  clavum  nsanu  sua  tenens  (Ort.  Medicin.  p.  724.) 

■j  Who  quotes  Hippocrates  for  the  idea  (Sect.  649.)  couched 
under  the  term  of  «i/!o*fa?s*-as. 

§ Animam  esse  Gubernatricem,  &c.  &c.  Oratio  de  anima 
Medica.  passim. 

||  Lug.  Batav.  Luchtman’s,  1745.  (Chap.  2.) 

«j[  Institutes  of  Medicine,  § 126  to  135.  “ From  what  has  been 
now  said  of  the  excitement  and  collapse  of  the  brain,  it  will  ap- 


AMERICAN  EDITION. 


XVII 


and  applied  to  practice,  in  his  chapter  on  vefarike, 
(Firft  Lines,  § r 544.  and  feq.)  as  well  as  the  obferva- 
rions  in  his  letter  on  the  recovery  of  perfons  drowned : 
(p.  4.)  “ Though  the  circulation  of  the  blood  is  necef- 
fary  to  the  fupport  of  life,  the  living  fcate  of  animals 
does  not  confift  in  that  alone,  but  efpecially  depends 
upon  a certain  condition  of  the  nerves  and  mufcular 
fibres,  by  which  they  are  fenfible  and  irritable,  and 
upon  which  the  adlicn  of  the  heart  itfeif  depends,”  See. 
And  alfo  the  remarks  on  the  effect  of  ftimuli  in  keeping 
up  the  adtion  and  energy  of  the  brain*  at  all  times,  in 
his  treatife  upon  the  materia  medica. 

John  Hunter  had  been  fpeculating  too  on  this 
fubjedt.  In  his  experiments  on  animals,  with  refpccl  to 
their  power  of  producing  heat,  he  has  brought  curious 
and  important  facts  to  view : though  his  reafoning  on 
them  is  in  fome  inftances  inccnclufive  and  exceptiona- 
ble, in  others  quite  unphilofophical.  This  enquiry  was 
intended  as  a counterpart  to  the  experiments  of  Blag- 
den,  and  his  affociates  in  the  heated  chamber,  on  the 
power  of  the  human  body  to  produce  cold  in  high 
temperatures.  He  afcribes  a great  deal,  throughout  his 
performance,  to  the  ftimulant  action  of  cold,  and  to 
the  exhauftion  of  the  whole  of  the  powers  of  life  in 
freezing  animals,  by  their  efforts  to  produce  heat ; he 
even  afcribes  the  attempt  of  his  poor  vidtim,  the  dor- 
moufe,  to  get  cut  of  the  veffel  in  which  he  was  to  be 
frozen  to  death,  to  the  roufing  of  animal  adtion  by  cold! 
He  feems  to  take  little  notice  of  the  vital  organs,  the 
fire-place  whence  the  confiitution  receives  its  warmth ; 
nor  regard  much  the  condition  of  the  refpiratory  func- 
tion in  any  of  the  creatures  he  operated  upon,  nor  the 
pain  they  endured,  and  the  changes  in  their  economy 
confecuent  upon  it.  The  experiments  on  the  egg, 

b frog, 

pear  that  we  suppose  life,  as  far  as  it  is  corporal,  to  consist  in  the  ex- 
citement of  the  nervous  system,  and  especially  of  the  brain,  which 
unites  the  different  parts,  and  forms  them  into  a whole.”  § 136. 

* Materia  Medica,  p.  67,  &c. 


Sviii  PREFACE  TO  THE 

frog,  eel  and  fnail,  may  be  as  well  explained  on  the 
idea  of  the  increafed  fufceptibility  of  impreffion,  pro- 
duced by  the  fubduCtion  of  ftimuli,  and  by  an  extra- 
ordinary exertion  of  the  refpiratory  organs  caufing  a 
greater  evolution  of  heat,  as  upon  the  author’s  hypo- 
thecs, which  may  be  fummoned  up  in  this  general 
eonclufion ; that  cold  produces  its  effect  in  fufpending 
the  voluntary  actions,,  by  acting  as  a fedative  to  a cer- 
tain point ; beyond  which  it  feems  to  act  as  a JiimuJant , 
exciting  the  animal  powers  to  exert  themfeives  for  felf- 
prefervation. 

It  will  be  evident  to  him  who  reflects  on  what  has- 
been  related,  that  the  Epicurean  Sectaries  en- 
tertained no  other  than  mechanical  notions  concerning 
the  production,  actions,  and  changes  of  bodies;  and 
that  Hippocrates  and  his  followers,  though  confi- 
derably  more  advanced  towards  the  truth,  had  gone  no 
farther  than  to  obferve  folitary  and  individual  tacts,  ar- 
range thefe  into  detached  fentences,  or  infulated  apho- 
rifms,  fometimesintirely  true,. and  fome  containing  only 
a mixture  of  truth ; or  frame  ftrange  and  whimfical 
hypothefes,  by  aid  ot  which,  as  general  principles,  they 
attempted  to  explain  things ; and  the  molt  forward  of 
them  feems  to  have  done  little  more  than  trace  the  cor- 
poreal functions,  by  partial  induction,  to  the  aio-S»Pf-is» 

zafio \iKov  Or  COMMON  SENSORY. 

. Such  was  the  condition  of  medical  fcience,  until 
nearly  twenty  years  ago,  when,  in  that  very  place  where 
fpcifm , reaction,  and  vis  medicairix  nature  were  flourifh- 
ing  in  full  vigour,  under  the  affiduous  cultivation  of 
Cullen,  they  were  nipped  and  cropped  in  the  blof- 
fom,  and  nearly  eradicated  as  noxious,  by  the  improv- 
ing hand  of  Brown.  From  the  intimate  acquaint- 
ance which  Brown,  or  Bruno,  as  he  called  himfelf, 
had  with  the  publifhed  writings,  and  probably  with 
the  private  opinions  of  Cullen;  from  his  academic 
habits,  his  erudition  and  knowledge  of  every  thing 
palling  at  the  Univerfity  of  Edinburgh,  he  muff 

have 


AMERICAN  EDITION. 


xix 


have  had  great  opportunities,  as  well  of  learning  all 
that  was  printed  in  phyfic,  as  of  fludying  the  de- 
feds,  and  detecting  the  weaknefs  of  that  profeffor’s 
dodrines.  He  told  the  writer  of  this  preface,  that 
he  ventured  one  day  to  talk  to  Cullen  on  the  incom- 
prehensible ideas  of  atony  and  fpaim  exiding  in  the 
fame  veffels  of  .the  body  at  the  fame  time,  and  thereby 
provoked  him  to  manifefl  figns  of  impatience  and  dif- 
pleafure.  A’coolnefs  took  place  immediately,  which 
increafed  at  laft,  by  fuccefiive  and  mutual  aggrava- 
tions, to  rooted  averfion  and  deep  opposition.  And 
to  this  irritated  date  of  Brown’s  mind,  indignant 
with  a fenfe  of  unbecoming  treatment,  is  to  be  afcrib- 
ed  no  fmall  portion  of  that  refolution  and  energy  with 
which  he  laboured  out  a Sydem  of  Medical  Philofo- 
phy,  which,  though  not  free  from  errors,  borrows, 
however,  none  from  Cullen. 

On  the  publication  and  contents  of  the  fird  edition 
of  the  Elementa  Medicinas  of  this  author  I lhali  be  a 
little  particular,  on  account  of  the  fcarcity  of  the  work, 
and  of  the  gratification  it  may  afford  to  an  enquiring 
mind  to  learn  the  progrefs  of  ufeful  difcoveries. 

It  was  published  in  1780,  and  was  dedicated  to  Sir 
John  Elliot;  but  this  dedication  was  withheld 
from  the  fecond  edition.  After  dating  his  twenty  years 
labour  in  learning  and  teaching  phyfic,  he  obferves,  it 
was  not  until  the  fourth  ludrum  that  fome  dawning 
of  light  broke  in  upon  him. 

The  opinion  that  in  the  phlegmafire  of  nofologids, 
local  affedtion  was  not  the  caufe  of  pyrexia,  but,  on 
the  contrary,  a fymptom  confequent  upon  a previous 
general  excitement  of  the  whole  conditution,  appears 
to  have  been  early  adopted  by  him ; and  from  his  own 
perfonal  fufferings  in  eryfipelas,  cynanche  tonfillaris, 
catarrh,  and  fynocha,  and  from  his  perufal  of  what- 
ever had  been  written  by  Morgagni,  Triller,  and 
other  candid  authors  on  thefe  fubjedts,  and  on  pneu- 
monia, he  was  confident  his  idea  was  right. 

He, 


XX 


PREFACE  TO  THE 


He,  at  this  time,  propofed  the  doctrine  of  cold  pre- 
diipofing  the  body  to  be  operated  upon  in  a pc  .verful  * 
manner,  and  to  a morbid  degree,  by  fubfequent  her  : ; 
which,  indeed,  may  be  regarded  as  one  of  the  mofi 
important  practical  truths  in  medicine. 

Pie  calls  in  queftion  the  propriety  of  forming  opi- 
nions of  the  nature  of  difeafes  by  their  iyrnptoms  mere- 
ly, and  boldly  adopts  the  method  of  judging  from  the 
“ Iredentia  and  juvantia." 

He  offers  well-founded  criticifm  on  nofological  a:- 

o _ _ 

rangement,  and  fhews  wherein,  through  want  of  dii- 
tmdtion  between  univerfal  and  local  difeafes,  a number 
of  thefe  had  been  claffed  wrong. 

On  examining  the  phlogiftic  exanthemata  he  con- 
tends, that  in  mealies  and  fcarlet  fever,  as  well  as  in 
fmali-pqx,  the  general  indication  of  cure  is  to  dimi- 
nilh  the  inflammatory  diathefis,  without  the  leait  re- 
gard to  the  particular  nature  of  the  contagion,  or  the 
ilage  of  eruption;  but  thefe  are  carefully  to  be  diilin- 
guilhed  from  the  plague,  and  other  eruptive  diieaies 
of  a totally  oppofite  character:  and  that  without  at- 
tending to  the  peculiarity  of  the  refpiration,  or  the  pre- 
cife  nature  of  the  morbific  caufe,  the  certain  things  to 
be  attended  to  are,  How  far  the  difeafed  condition  de- 
viates from  health  ; and  in  wlut  degree  the  living  body 
appreximates  towards  death.  The  exanther, '.atom 
fymptoms  in  the  two  clafies  of  complaints,  varying  in 
each,  their  form  only,  and  not  their  nature. 

Having  proceeded  thus  far,  lie  declares  that  difeafes 
of  the  fame  type  or  clafs  arc  to  be  relieved,  or  cured, 
by  the  fame  mode  of  treatment;  and  that  the  volumes 
of  diagnostics,  and  the  endleis  distinctions  of  nol'ologv, 
in  fpite  of  the  authority  of  even  Baglivi  and  Sy- 
denham, when  opoofed  to  clear  reafon  and  matter  of 
fact,  ought  to  be  ciifregarded.  He  expreffes  his  an- 
prehenfions  too,  left  the  infinite  diftindtion  ot  diieaies 
lhould  lead  to  a mode  of  practice  equaliv  diverfified, 
and  have  a very  baneful  effect  upon  materia  medica 
and  preferiptions. 


In 


AMERICAN  EDITION. 


xxi 


In  his  remarks  upon  predifpofition  to  bad  health, 
he  avers  that  no  perfon  ever  fuddenly  became  tick,  but 
that  gradually  a predifpofition  was  created  by  the  agen- 
cy of  the  exciting  powers,  and  out  of  this  predifpofi- 
tion grew  the  difeafe.  Of  this  he  gives  examples  in 
the  phlogiftic  exanthemata,  wherein  he  lays,  a high 
degree  of  excitement  produces  the  difeafe,  a lower  pre- 
difpofition, and  a {till  lower  health : the  means,  there- 
fore, conducive  to  the  latter  of  thefe  he  thinks  fo  fim- 
ple,  that  the  ufe  of  the  common  ncfology  is  intirely 
fuperfeded. 

Proceeding  upon  this  plan,  he  diftinguifhes  local 
from  univerfal  ailments ; both  of  which  are  confufediy 
claffed  together,  in  the  different  nofological  arrange- 
ments. 

This  led  him  to  an  examination  of  hemorrhagy, 
which,  if  attended  in  the  beginning  with  phlogiftic 
diathefis,  he  thought  always  became  eventually  afthe- 
nic,  and  in  this  enquiry  it  was  that  he  was  induced  to 
call  in  queftion  the  exiftence  ot  plethora,  as  a caufe  of 
hemorrhagy,  and  to  rejecft  altogether  the  notion  of  a 
vis  medicatrix  naturre  as  an  agent  in  the  animal  fyftem. 

This  firft  edition  of  the  Eiementa  is  an  unfinifned 
work,  and  comprehends  the  details  of  his  doftrine  no 
farther  than  the  fihenic  form  of  difeafes.  Among  thefe 
he  there  ranks  hemorrhagy,  efpecially  menorrhagia, 
hrermorhois,  epiftaxis,  and  apoplexy ; an  arrangement 
which  he  afterward  confidered  wrong,  and  altered  ac- 
cordingly in  the  following  editions,  by  placing  them  all 
in  the  afthenic  clafs. 

Such,  he  tells  us,  was  the  train  of  ideas  pafiing  in 
his  mind  as  he  refledted  upon  the  animal  economy ; and 
upon  thefe  confiderations  did  he  judge  himfeif  war- 
ranted in  undertaking  an  explanation  of  the  fubject, 
different  in  many  refpects  from  any  thing  done  before 
him. 

Ke  declares,  throughout  the  whole,  he  never  de- 
fcends  beneath  his  dignity  to  animadvert  uoon  particu- 
lar 


xxii  PREFACE  TO  THE 

lar  per  Jons  ; though  in  certain  cafes,  where  almoft  im- 
plicit faith  and  idolatrous  reverence  had  been  given  to 
certain  authors,  he  Iras  freely  attacked  and  refuted  their 
opinions.  Fie  apologizes  for  the  plainnefs  of  ftile  and 
manner  with  which  the  performance  is  written,  efpe- 
cially,  fmce  to  avoid  the  contagion  of  opinion,  he  had 
read  no  medical  book  for  five  whole  years,  and  had 
fcarcely  confulted  the  monuments  of  ancient  elegance 
for  twenty. 

There  is  a great  deal  of  animation  and  force  in  his 
argument  againft  plethora,  from  the  ninety-fourth  to 
the  ninety-eighth  feCtion,  which  he  concludes  with 
this  challenge : “ Si  fit  quod  ad  hoc  refpondeas,  re- 
fponde  Stahli  aut  jube  Junckerum.” 

In  the  hundred  and  fourth fection  he  oppofes,  in  de- 
cided terms,  the  tonic  or  aftringcnt  operation  of  cold, 
particularly  as  caufing  conftriction  of  the  fkinj  and 
repeats  the  fame  in  feveral  places,  (§  18c — 182.)  de? 
nying  that  it  afts  as  a ftimulant. 

In  his  reafoning  againft  lentor  in  the  fluids  as  a caufe 
of  difeafe,.  he  breaks  cut  into  the  following  fpirited 
exclamation : “ Quam  infelix  ea  pathologia  eft ! cuius 
perpetuum  principium,  quod  univerfis  ccmprehenfis 
partibus  convenire,  univerfas  illuflrare,  ct  explicare 
debet,  ne  uni  quidern  convenit,  unam  illuftrat,  unara 
explicat,  contra  omnibus  repugnat,  omnes  obfcurat, 
et  confundit and,  rejecting  the  pathology  of  th.e 
fluids,  declares,  that  cool  water,  pure  air,  wine,  and 
Peruvian  bark  refill  putrifadlion  in  no  other  way  than 
by  keeping  up  excitement. 

In  his  remarks  upon  fpafm,  he  endeavours  to  (hew 
that  it  cannot  be  a caufe  of  difeafe,  either  of  the  fthe- 
nic  or  aflhenic  kind,  and  ought,  of  courfe,  to  be  re- 
jected from  both,  as  fhould  alfo  what  has  been  called 
the  reaction  of  thefyjlem , in  fever.  In  the  courfe  of  his 
animated  argument,  he  afks  if,  toward  the  end  of  the 
eighteenth  century,  “ quis,  opinionem  meram,  nulla 
rationis,  nulla  veri  vel  tenuifiima  umbra  commenda- 

tam, 


AMERICAN  EDITION. 


xxiii 

ram,  folidiffimis  arguments,  item  ipfi  tuercfe  adhibitis 
compertam  falfam,  poftvanam  omni  falfer  logics  genere 
defenfionem,  pro  re  vera  et  certa  oblatum  iri  crederet  r” 

He  is  eveiy  where  oppofed  to  that  clafiification  and 
arrangement  of  difeafes  which  has  lb  much  obtained 
of  late,  and  clofes  this  work  with  the  words,  “ Nofo- 
logia  delenda.” 

He  publMhed  a fecond  edition  in  the  year  1784, 
and  added  thereto  the  afthenic  clafs  of  difeafes. 
Taught,  by  experience  and  obfervation,  in  the  dif- 
ferent forms  of  the  gout  and  afthma,  of  the  benefit 
of  ftimulant  remedies,  he  had  no  hefitation  to  confider 
them  among  the  effects  of  weaknefs ; as  were  likewife 
fevers  ftridtly  fo  called  (febres)  both  intermittent  and 
continued,  and  all  the  kinds  of  hemorrhagy,  &c.  In 
fhort,  the  confideration  of  the  difeafes  not  belonging 
to  the  fthenic  clafs,  convinced  him  they  muff  be  re- 
ferred to  the  afthenic ; fuch  were  all  fpafmodic  or  con- 
vulfive  ailments,  dyfpepfia,  and  other  the  like  affec- 
tions of  the  alimentary  canal,  and  the  greater  part  of 
the  maladies  of  children. 

In  this  performance  too,  he  contends  againft  the 
advocates  for  fedatives.  Opium,  he  declares,  has  a fti- 
mulant operation ; colds  or  catarrhs  are  produced  by 
heat  fucceeding  to  cold,  and  not  vice  verfa  j and  ex- 
tends his  laws  of  animation  to  the  vegetable  creation. 

In  fhort,  he  concluded  there  was  in  the  medullary- 
nervous  matter,  and  mufcular  folid  of  living  bodies, 
which  have  been  generally  called  the  nervous  fyftem, 
a property  by  which  they  could  be  affected  by  outward 
agents,  as  well  as  by  their  own  functions,  in  fuch  a 
way  as  to  produce  the  phenomena  peculiar  to  the  liv- 
ing ftate.  This  capacity  of  being  adted  upon  is  term- 
ed excitability , and  the  agents  are  all  denominated 
Jlimulants,  while  the  effect  produced  by  the  operation 
of  ftimulants  upon  excitability  is  called  excitement. 

Excitement  is  terminated  in  two  ways.  1.  By  the 
exhauftion  of  excitability,  through  the  violence  or  con- 
tinuance- 


PREFACE  TO  THE 


xx  iv 

tinuance  of  ftimulus,  which  is  called  indirect  debilii). 
2.  By  the  accumulation  of  excitability,  through  defi- 
cient ftimulus,  which  is  termed  direct  debility.  Be- 
tween the  two  extremes  of  indirect  and  diredt  debility 
are  experienced  both  health  and  difeafes  of  the  fthenic 
kind,  or  thofe  febrile  complaints  (pyrexim,)  accom- 
panied with  what  has  been  called  phlogiftic  diathefls, 
wherein,  though  the  excitement  confiderably  exceeds 
the  healthy  rate,  ftill  it  does  not  reach  the  limits  ot 
indiredt  debility. 

Stimuli  lofe  their  efficacy  after  long  and  frequent  ap- 
plication ; but  even  then  the  excitability,  exhaufted  in 
relation  to  one  ftimulus,  is  capable  of  being  added  upon 
by  another. 

Therefore,  the  wafte  of  excitability,  after  exhaufticn 
of  one  ftimulus  after  another,  is  very  hard  to  be  re- 
paired, by  reafen  of  the  difficulty  of  accefs  to  frefin 
ftimuli  to  work  upon  the  languifhing  excitability; 
which,  by  being  applied  ftrong  at  firft,  and  gradually 
weakened  aftenvards,  anfwers  the  purpofe;  and  alio 
the  fuperabundant  excitability  left  by  mbdudtion  of 
one  ftimulus  after  another,  produces  fuch  an  excitable 
condition  of  the  fyftem,  that  much  nicety  is  requiiite 
to  wear  it  gradually  away  by  application  of  very  weak 
ftimuli  at  firft,  and  by  degrees  ftronger  and  ftronger, 
until  the  accuftomed  ones  can  be  comfortably  borne. 
According  to  the  Brunonian  Doctrine  difeafes  appear 
under  various  modifications,  as  exhibited  in  the  tabic 
below'. 

T hus  they  may  be, 

1 . Univerfal,  fuch  as  primarily  affect  the  whole 
conftitution,  as  fevers,  &c. 

2.  Local,  where,  from  limited  morbid  affedtion, 
a particular  part  labours,  without  difordering  the 
intire  habit ; as  trifling  wounds,  phlegmons,  See. 

3.  Loco-uni verfal,  when,  from  a local  affection,  the 
whole  body  is  eventually  brought  into  a difeaied 
condition;  as  in  lues  originating  from  chancre, 
fmall-pox  from  inoculation,  &c. 


4.  LTniverfo- 


AMERICAN  EDITION. 


XXV 


4.  Univerfo-local;  as  if  after  a general  ailment  any 
particular  part  or  organ  is  affedted  in  a fecondary 
way ; as  the  eruptions  of  exanthematous  pyrexire, 
fyphilitic  blotches,  &c. 

And  each  of  thefe  forms  of  difeafes  muff  eonfift 
either  in, 

1 . Direct  debility ; as  in  fcurvy,  hunger,  cold,  &c. 

2.  Sthenic  diathefis*  as  in  pieurify,  other  forms  of 
fynocha,  &c. 

3.  Indirect  debility ; as  in  old  age,  intoxication,  fa- 
tigue, &c. 

4.  Diredt  debility  added  to  indirect ; as  in  gout  very 
often,  and  in  many  difeafes  of  advanced  life. 

3.  Indirect  debility  added  to  direct ; as  in  over-feed- 
ing a famifhed  perion,  &c.  in  molt  difeafes  of 
infants  and  young  perfons. 

Let  now  the  candid  reader  compare  this  view  with 
the  opinions  of  the  old  Methodists,  and  fay,  whe- 
ther it  be  a mere  revival  of  the  practice  of  Them i son 
and  Thessalus?  Surely  they  who  have  afferted  it 
was,  can  never  be  luppofed  to  have  given  themfelves 
the  trouble  to  examine. 

Yet,  with  all  this  novelty  about  it,  Brown’s  doc- 
trine wants  precifion.  It  proceeds  not  far  enough  be- 
yond general  principles,  which,  by  reafon  of  their  ab- 
ftradt  or  fpeculative  nature,  have  not  been  found  clofely 
enough  applicable  to  the  fubjects  of  pathology  and 
phyfiology — He  takes  for  granted,  for  inftance,  that 
the  nervous  fyftem  is  always  one  and  the  fame  excitable 
thing.  He  fays  fcarcely  any  . thing  accurate  on  the 
different  qualities  of  the  blood  and  circulating  fluids, 
and  of  the  fecretions ; and  gives  nothing  very  minute 
concerning  the  mighty  influence  of  the  respiratory  and 
digeftive  proceffes  upon  the  animal  oeconomy.  He 
palfes  over  entirely  the  chemical  compoution  of  our 
food  and  drink,  of  our  inhalations  and  excretions,  of  the 
gafes  we  breathe  and  the  remedies  we  fwallow : in  fhort, 
he  has  left  not  a fentence  on  the  compofition  or  the  na- 

c ture 


XXVI 


PREFACE  TO  THE 


ture  of  bone,  mufcle,  veffel,  fat,  lymph,  or  gluten,- 
nor  how  varioufly  thefe  are  affeCted  by  difeafe,  nor  in 
what  their  healthy  differs  from  their  morbid  ftate,  nor 
by  what  means  the  alterations  they  undergo  are  brought 
about. 

Thefe,  and  other  omiflions  and  defeats  in  the  Bru- 
nonian  System,  called  for  amendment;  and  this 
was  to  be  begun  by  attending  to  the  varying  condition 
of  the  living  folid,  and  the  concomitant  ftate  of  the 
fluids. 

The  eftabliftiment  of  the  new  nomenclature  of 
chemiftry  in  France,  in  1787,  maybe  confidered  as 
forming  a new  epoch  in  fcience.  Since  the  publica- 
tion of  that  invaluable  performance,  language  has  been 
adapted  with  greater  accuracy  to  the  expreflion  of 
ideas,  and  philofophical  inveftigation  conducted  with 
fuperior  advantage  and  fuccefs.  Lavoisier,  in 
his  Elements  of  Chemiftry,  has  attempted  the  ex- 
planation of  the  putrefactive,  as  well  as  the  fermenta- 
tive procefs  in  the  organized  forms  of  animals  and  of 
plants,  upon  the  modern  principles;  and,  in  a natural 
and  convincing  manner,  has  proceeded  a great  way 
beyond  any  one  who  undertook  the  explanation  be  • 
fore.  Spallanzani  indeed,  in  his  Experiments  on 
the  ConcoCtion  of  Food  in  the  Stomach,  and  Craw- 
ford, in  his  Application  of  the  Principles  of  Com- 
buftion  to  the  Function  of  the  Lungs  in  breathing, 
v had  given  excellent  fpecimens  of  this  mode  of  reafon- 
ing  on  phyfiological  lubjeCts.  Great  progrefs  has  been 
made  fince  in  detecting  the  nature  and  properties  of 
the  atmofphere,  the  gales  and  seriform  fluids ; and  the 
right  knowledge  of  thefe,  derived  from  experiment 
and  obfervation,  has  furnifhed  the  means  of  expound- 
ing many  of  the  animal  functions,  in  a plain  and  happy 
manner. 

W e do  not  merely  know,  as  Prieftley  and  Scheele 
did,  that  there  is  a gafeous  production,  pure  air,  ne- 
ceffary  to  the  prefervation  and  continuance  of  animal 

life ; 


AMERICAN  EDITION.  xxvii 

life  ; but  we  think  we  know  it  is  a compound  fub- 
ftance,  and  what  its  compound  ingredients  are;  we 
believe  we  can  make  and  unmake  it  artificially,  and 
that  nature  is  doing  fo  inceifantly : we  think  the  term 
“ dephlogifticated  air”  not  accurately  nor  logically  ap- 
plied; but,  judging  from  its  tendency  to  produce 
fournefs  when  combined  with  other  bodies,  we  call 
the  bafis  of  it  “ the  acidifying  principle,”  and  the 
combination  of  that  bafe  with  light  and  caloric,  or 
the  matter  of  heat,  “ oxygene  gas  or  air.” 

From  noting  the  operation  of  this  oxygene , or  prin- 
ciple of  fouring,  upon  various  bodies,  we  imagine  we 
know  the  compofition  of  acids,  and  have  made  out  a 
.confiderable  lift  of  acidifiable  bafes ; fo  that  the  format 
tion  of  fixed  air  from  oxygene  and  carbone,  or  char- 
coal, of  nitrous  acid  from  it  and  azote,  of  vitriolic 
acid  from  the  fame  and  fulphur,  and  phofphoric  acid 
from  its  union  with  phofphorus,  feem  to  be  well  efta- 
blilhed  truths.  We  imagine  that  a certain  other  clafs 
of  bodies  capable  of  combining  with  oxygene,  but 
not  to  the  point  of  acidity,  forms  thereby  half-acids 
or  oxydes,  and  that  thus  the  calces  of  metals,  animal 
blood  and  fecretions,  as  well  as  the  farinaceous,  gum- 
my, and  mucilaginous  parts  of  plants,  are  formed. 

We  think  the  compofition  of  water  is  underfliood, 
and  inftead  of  being  an  elementary  body,  as  was  for- 
merly believed,  that  it  is,  in  fadt,  but  the  oxyde  of 
hydrogen,  or  a combination  of  this  latter  fubftance 
with  the  principle  of  acidity,  but  not  to  the  fouring 
point. 

It  is  confidered  alfo,  that  more  is  known  concern- 
ing the  compofition  of  the  irritable  fibre,  of  the  adi- 
pofe  matter,  and  of  the  bones : and  that  the  effects 
produced  upon  the  circulated  fluids  by  breathing,  and 
through  them  upon  the  folids  of  the  animal  body  in 
health,  and  the  alterations  too  that  the  liquid  and  firm 
parts  undergo  by  impeding,  vitiating,  or  obftru cling 
that  function,  in  ordinary  cafes,  as  well  as  in  gravid 

females* 


xxviii  PREFACE  TO  THE 

females,  are  now  better  comprehended  than  they  ufed 
to  be.  Jnafmuch,  that,  after  the  great  light  thrown 
upon  this  fubject  by  Goodwin,  Girtanner  has 
been  enabled  to  drefs  up  the  Brunonian  Syftem  in  the 
more  recent  faihion,  and  Beddoes,  to  fupply  and 
adcrn  it  with  aimoft  all  that  was  wanting  to  make  it 
additionally  engaging  and  attractive.  Subtncrlion, 
consumption,  leurvy,  ftone,  catarrh,  obefity,  dropfy, 
and  fever,  have  already  received  great  elucidation,  both 
in  theory  and  practice,  from  the  application  of  che- 
mical principles ; and  we  may  reafonably  hope,  that 
before  many  more  years  elapfe,  better  and  more  cor- 
re<5t  ideas  will  be  entertained  of  many  articles  of  the 
materia  medica,  and  of  their  manner  of  operating; 
that  a new  medical  nomenclature  (than  which  nothing 
in  fcience  is  more  wanting)  will  be  made  out ; and  that, 
from  the  ascertained  condition  of  the  body,  and  the 
known  compoiition  and  operation  of  remedies,  phyfi- 
cians  may  prefcribe  fairly  for  the  adtual  ftate  of  the 
conftitution,  and  the  removal  of  the  prefent  malady, 
without  being  milled,  as  too  often  happens  at  prefent, 
by  fpecious  words,  and  idle  or  deceitful  names. 

But,  notwithftanding  the  many  and  beautiful  ap- 
plications of  chemical  principles  to  the  explanation  cf 
the  animal  functions,  we  are  not  to  imagine  every 
thing  in  life  fufceptible  of  chemical  interpretation. 
What  it  is  that  enables  the  atoms  composing  a mufcle 
to  cohere,  and  the  mufcle  to  contract  and  perform 
great  exertions  cf  ftrength,  we  know  not ; but  this 
we  know  very  well,  that  we  can  never  form  a mulcle 
by  fyntheis,  or  the  putting  together,  in  any  artificial 
form,  thole  fubftances  which  appear,  from  analyfis,  to 
conftitute  a mulcle.  There  is  fomething  in  animated 
exiftence,  which  eludes  our  moft  abtive  relearches, 
and  which  defies  fub million  to  either  mechanical  or 
chemical,  lav/s.  With  r'dpect  to  chemical  modes  of 
reasoning  upon  thefe  fubjedls,  it  is  obfervable,  that 
they  apply,  with  their  grcateft  extent  and  accuracy, 

to 


AMERICAN  EDITION. 


XXIX 


to  fuch  parts  of  the  body  as  have  the  lowed:  degrees 
of  animation,  as  the  teeth,  bones,  fat,  and,  generally 
fpeaking,  the  circulated  and  fecreted  fluids ; while  the 
qualities  of  mufcular  fibres,  by  which  they  become 
contractile,  and  of  nervous  expanfions,  whereby  they 
take  on  fenfation,  with  the  whole  of  the  functions 
arifing  fibm  irritability  and  fenfibility,  are  referable  to 
other  and  different  laws. 

The  inveftigation  of  thefe  Laws  of  Organic  Life  is 
attempted  by  our  learned  and  very  ingenious  author 
in  the  following  work.  The  Zoonomia,  therefore, 
though  not  exempt  from  fanciful  and  vifionary  doc- 
trines, prefents  confiderations  of  the  firft  importance, 
both  to  the  fpeculative  philofopher  and  the  practical 
phyfician ; to  him  who  contemplates  the  operations  of 
mind  as  a fcience,  or  to  him  that  attends  to  the  cor- 
poreal functions  as  an  artiffc.  How  far  Dr.  Darwin 
has  fucceeded,  and  how  much  ftill  remains  to  be  done 
on  this  fubjedt,  it  may  not  perhaps  be  eafy  to  fay,  efpe- 
cially  fince  his  fecond  volume  has  not  yet  reached  us ; 
but  I have  no  hefitation,  from  a confideration  of  the 
prefent  work,  to  recommend  it  warmly  to  the  perufal 
of  ftudents,  and  efpecially  of  beginners,  whofe  unbi- 
afed  minds  will  receive  and  comprehend  its  interefting 
contents,  with  lefs  difficulty  than  thofe  already  occu- 
pied by  pre-conceptions  and  prejudices. 

SAMUEL  L.  MITCHILL. 


Planclome , June  20,  1 796. 


, - 

. ■ 

■ r * 


..  i • 1 


t = 


, 


' ■' 


T O 


ERASMUS  DARWIN, 

ON  HIS  WORK  ENTITLED 

Z 0 0 N 0 M I A, 

B}  DEwHURST  BILSBORROW. 


H.AIL  to  the  Bard!  who  sung,  from  Chaos  hurl’d 
How  suns  and  planets  form’d  the  whirling  world ; 

How  sphere  on  sphere  Earth’s  hidden  strata  bend, 

And  caves  of  rock  her  central  fires  defend ; 

Where  gems  new-born  their  twinkling  eyes  unfold,  £ 

And  young  ores  shoot  in  arborescent  gold. 

How  the  fair  Fiower,  by  Zephyr  woo’d,  unfurls 
Its  panting  leaves,  and  waves  its  azure  curls; 

Or  spreads,  in  gay  undress,  its  lucid  form, 

To  meet  the  sun,  and  shuts  it  to  the  storm;  io 

While  in  green  veins  impassion’d  eddies  move. 

And  Beauty  kindles  into  life  and  love. 

How  the  first  embryon-fibre,  sphere,  or  cube, 

Lives  in  new  forms, — a line, — a ring, — a tube; 

Closed  in  the  womb  with  limbs  unfinish’d  laves,  1 5 

Sips  with  rude  mouth  the  salutary  waves; 

Seeks  round  its  cell  the  sanguine  streams  that  pass. 

And  drinks,  with  crimson  gills,  the  vital  gas; 

Weaves  with  soft  threads  the  blue  meandering  vein, 

The  heart’s  red  concave,  and  the  silver  brain;  20 

Leads  the  long  nerve,  expands  the  impatient  sense. 

And  clothes  in  silken  skin  the  nascent  Ens. 

Erewhile,  emerging  from  its  liquid  bed, 

It  lifts  in  gelid  air  its  nodding  head; 

The  light’s  first  dawn  with  trembling  eye-lid  hails,  25 

With  lungs  untaught  arrests  the  balmy  gales; 

Tries  its  new  tongue  in  tones  unknown,  and  hears 
The  strange  vibrations  with  unpractised  ears; 

Seeks  with  spread  hands  the  bosom’s  velvet  orbs, 

With  closing  lips  the  milky  fount  absorbs;  30 

And, 


xxxii  TO  ERASMUS  DARWIN. 

And,  as  compress’d  the  dulcet  streams  distil. 

Drinks  warmth  and  fragrance  from  the  living  rill ; 

Eyes  with  mute  rapture  every  waving  line, 

Prints  with  adoring  kiss  the  Paphian  shrine, 

And  learns  ere  long  the  perfedf  form  confess’d,  3 j 

Ideal  Beauty  from  its  mother’s  breast. 

Now  in  strong  lines,  with  bolder  tints  design’d, 

You  sketch  ideas,  and  pourtray  the  mind; 

Teach  how  line  atoms  of  impinging  light 

To  ceaseless  change  the  visual  sense  excite;  40 

While  the  bright  lens  collefts  the  rays,  that  swerve. 

And  bends  their  focus  on  the  moving  nerve : 

How  thoughts  to  thoughts  are  link’d  with  viewless  chains, 
Tribes  leading  tribes,  and  trains  pursuing  trains; 

With  shadowy  trident  how  Volition  guides,  45 

Surge  after  surge,  his  intellectual  tides; 

Or,  Queen  of  Sleep,  Imagination  roves 
With  frantic  Sorrows,  or  delirious  Loves. 

Go  on,  O Friend!  explore  with  eagle-eye, 

Where  wrapp’d  in  night  retiring  causes  lie : 50 

Trace  their  slight  bands,  their  secret  haunts  betray. 

And  give  new  wonders  to  the  beam  of  day ; 

Till,  link  by  link  with  step  aspiring  trod, 

You  climb  from  Nature  to  the  throne  of  God. 

So  saw  the  Patriarch  with  admiring  eyes  5 5 

From  earth  to  heaven  a golden  ladder  rise ; 

Involved  in  clouds  the  mystic  scale  ascends, 

And  brutes  and  angels  crowd  the  distant  ends. 

Trin.  Col.  Cambridge , Jan.  1,  1794. 


REFERENCES  TO  THE  WORK. 


Botanic  Garden , Part  I. 
Line  1 
3 


Canto  I. 
IV 


1. 105. 
I.402. 
I.  1. 140. 

III.  I.401. 

IV.  I.452. 
I.  1.  14. 


Zoonoiuia. 


12.  Seel.  XIII. 

■13. XXXIX.4.1.- 


Line  18 
26 

3° 

36 

38 

43 

44 

— ' 45 

47 

5° 

-51 
-54 


Sett.  XVI.  2.  and  XXXVIII 

-XVI.  4. 

XVI.  4. 

XVI.  6. 

III.  and  VII. 

X. 

XVIII.  17. 

XVII.  3.  7. 

XVIII.  8. 

XXXIX.  4.  8. 

XXXIX.  the  Motto. 

XXXIX.  8. 


PREFACE. 


The  purport  of  the  following  pages  is  an  endeavour  to  re- 
duce the  fadts  belonging  to  Animal  Life  into  clafles,  or- 
ders, genera,  and  fpecies ; and,  by  comparing  them  with  each 
other,  to  unravel  the  theory  of  difeafes.  It  happened,  perhaps 
unfortunately  for  the  inquirers  into  the  knowledge  of  difeafes, 
that  other  fciences  had  received  improvement  previous  to  their 
own ; whence,  inftead  of  comparing  the  properties  belonging 
to  animated  nature  with  each  other,  they,  idly  ingenious,  bufied 
themfelves  in  attempting  to  explain  the  laws  of  life  by  thofe  of 
mechanifm  and  chemiftry ; they  confidered  the  body  as  an  hy- 
draulic machine,  and  the  fluids  as  pafling  through  a feries  of 
chemical  changes,  forgetting  that  animation  was  its  eflential 
charadteriftic. 

The  great  Creator  of  all  things  has  infinitely  diverfified 
the  works  of  his  hands,  but  has  at  the  fame  time  damped  a cer- 
tain iimilitude. on  the  features  of  nature,  that  demonftrates  to 
us,  that  the  whole  is  one  family  of  one  parent.  On  this  limi- 
litude  is  founded  all  rational  analogy ; which,  fo  long  as  it  is 
concerned  in  comparing  the  eflential  properties  of  bodies,  leads 
us  to  many  and  important  difcoveries ; but  when  with  licentious 
activity  it  links  together  objects,  otherwife  difcordant,  by  fome 
fanciful  fimilitude,  it  may  indeed  colledt  ornaments  for  wit  and 
poetry,  but  philofophy  and  truth  recoil  from  its  combinations. 

The  want  of  a theory,  deduced  from  fuch  ftridt  analogy, 
to  condudl  the  pradtice  ot  medicine,  is  lamented  by  its  profeflors  - 
for,  as  a great  number  of  unconnected  facts  are  difficult  to  be 
acquired,  and  to  be  reafoned  from,  rhe  art  of  medicine  is  in 
many  inftances  lefs  efficacious  under  the  diredtion  of  its  wifeft 
pradtidoners ; and  by  that  bufy  crowd,  who  either  boldly  wade- 
in  darknefs,  or  are  led  into  endlefs  error  by  the  glare  of  falfe 
dieory,  it  is  daily  pradtifed  to  the  deftrudtion  of  thoufands ; add 
to  this  the  unceafing  injury  which  accrues  to  the  public  by  the 
perpetual  advertifements  of  pretended  noftrums ; the  minds  of 
the  indolent  become  fuperftitioufly  fearful  of  difeafes,  which 

B they 


a PREFACE. 

they  do  not  labour  under ; and  thus  become  the  daily  prey  of 
fome  crafty  empyric. 

A theory  founded  upon  nature,  that  fhould  bind  together  the 
Scattered  facts  ot  medical  knowledge,  and  converge  into  one 
point  ol  view  the  laws  ot  organic  life,  would  thus  on  many 
accounts  contribute  to  the  intereft  of  fociety.  It  would  capa- 
citate men  ot  moderate  abilities  to  pradtife  the  art  of  healing 
with  real  advantage  to  the  public ; it  would  enable  every  one  of 
literary  acquirements  to  diftinguifh  the  genuine  difciples  of  me- 
dicine from  thofe  of  boafttul  effrontery,  or  of  wilv  addrefs: 
and  would  teach  mankind  in  fome  important  fituations  the 
knowledge  of  therrtf elves. 

There  are  fome  modem  practitioners  who  declaim  again  ft 
medical  theory  in  general,  not  confidering  that  to  drink  is  to 
theorize ; and  that  no  one  can  diredt  a method  o!  cure  to  a per- 
fon  labouring  under  difeafe  without  thinking,  that  is,  without, 
theorizing ; and  happy  therefore  is  the  patient,  whole  phyfician 
poffeffes  the  beft  theoiy. 

The  words  idea,  perception,  fenfaricn,  recollection,  fug- 
geftion,  and  affoeiation,  are  each  of  them  ufed  in  diis  treatife 
in  a more  limited  fenfe  dian  in  the  writers  of  metaphyfic.  The 
author  was  in  doubt,  whedrer  he  fhould  rather  have  lubftiruted 
new  words  inftead  of  diem;  but  was  at  lengdi  of  opinion, 
that  new  definitions  ot  words  already  in  ufe  would  be  lefs 
burthenfome  to  the  memory  of  the  reader. 

A great  part  of  this  work  has  lain  by  die  writer  above 
twenty  years,  as  fome  of  his  friends  can  teftify  : he  had  hoped 
bv  frequent  revifion  to  have  made  it  wordiy  the  acceptance 
of  the  public ; this  however  his  odier  perpetual  occupations 
have  in  part  prevented,  and  may  continue  to  prevent,  as  long 
as  he  may  be  capable  of  revifmg  it ; he  therefore  begs  of  die 
candid  reader  to  accept  of  it  in  its  prefent  ftate,  and  to  excufe 
any  inaccuracies  ol  expreffion,  or  ol  conclufion,  into  which 
die  intricacy  of  his  fubjeeft,  the  general  imperfection  of  lan- 
guage, or  the  frailty  he  has  in  common  with  other  men,  ma\ 
have  betrayed  him ; and  from  which  he  has  not  die  vanity  to 
believe  this  treatife  to  be  exempt. 


zoonomia: 


Z O O N O M I A 


SECT.  I. 

OF  MOTION. 

The  whole  of  nature  may  be  fuppofed  to  confift  of 
twp  effences  or  fubftances ; one  of  which  may  he  termed  fpirit, 
and  the  other  matter.  The  former  of  thefe  poflefTes  the  power 
to  commence  or  produce  motion,  and  die  latter  to  receive  and 
communicate  it.  So  that  motion,  ccnfidered  as  a caufe,  imme- 
diately precedes  every  effedd  and,  confidered  as  an  effect,  it 
immediately  fucceeds  every  caufe. 

The  motions  of  matter  may  bedivided  into  two  kinds, 
primary  and  fecondary.  The  fecondary  motions  are  thofe 
which  are  given  to  or  received  from  other  matter  in  motion. 
Their  laws  have  been  iuccefsfully  inveftigated  by  philofophers 
in  dieir  treatifes  on  mechanic  powers.  Thefe  motions  are  dif- 
tinguifhed  by  this  circumftance,  that  the  velocity  multiplied 
into  the  quantity  of  matter  of  the  body  added  upon,  is  equal 
to  the  velocity  multiplied  into  the  quantity  of  matter  of  the 
adding  body. 

The  primary  motions  of  matter  may  be  divided  into  diree 
claffes,  thofe  belonging  to  gravitation,  to  chemiftry,  and  to 
life ; and  each  clafs  has  its  peculiar  laws.  Though  thefe  three 
dalles  include  the  motions  of  folid,  liquid,  and  aerial  bodies ; 
there  is  neverthelefs  a fourth  divilion  of  motions ; I mean  thofe 
of  the  fuppofed  ethereal  fluids  of  magnet! fm,  eleddricity,  heat, 
and  light ; whofe  properties  are  not  fo  well  inveftigated  as  to 
be  clafled  with  fufficient  accuracy. 

i ft.  The  gravitating  motions  include  the  annual  and  diurnal 
rotation  of  the  earth  and  planets,  the  flux  and  reflux  of  the 
ocean,  the  defeent  of  heavy  bodies,  and  other  phenomena  of 
gravitation.  The  unparalleled  fa gacity  of  the  great  Newton 
has  deduced  the  laws  of  this  clafs  of  motions  from  the  Ample 
prnciple  of  the  general  attraddion  of  matter.  Thefe  motions 
are  diftinguifhed  by  their  tendency  to  cr  from  the  centers  of 
the  fun  or  planets. 

2 d.  The  chemical  clafs  of  motions  includes  all  the  various 
appearances  of  chemiftn  . Many  of  the  fadds,  which  belong 


4 DEFINITIONS.  Sect.  II.  i. 

to  thefe  branches  of  fcience,  are  nicely  afcertained,  and  ele- 
gantly claffed ; but  their  laws  have  not  yet  been  developed  from 
Inch  fimple  principles  as  dime  above-mentioned;  though  it  is 
probable,  that  they  depend  on  the  fpecihc  attractions  belong- 
ing to  the  particles  of  bodies,  or  to  the  difference  of  the  quan- 
tity of  attradlion  belonging  to  the  tides  and  angles  of  thofe  par- 
ticles. The  chemical  motions  are  diftinguifhed  by  their  being 
generally  attended  with  an  evident  decompolition  or  new  com- 
bination of  the  a (Stive  materials. 

The  third  clafs  includes  all  the  motions  of  the  animal 
and  vegetable  world ; as  well  thofe  of  the  veffels,  which  cir- 
culate their  juices,  and  of  the  mufcles,  which  perform  uieir 
locomotion,  as  thofe  of  the  organs  of  fenfe,  which  conftitutc 
their  ideas. 

This  laid:  clafs  of  motion  is  the  fubject  of  the  following 
pages,  which,  though  confcious  of  their  many  imperfections, 
I hope  may  give  fome  pleafure  to  the  patient  reader,  and  contri- 
bute fomething  to  the  knowledge  and  to  the  cure  of  difeafes. 


' SECT.  II.  i. 

EXPLANATIONS  AND  DEFINITIONS. 

I.  Outline  of  the  animal  economy . — II.  I.  Of  the  fenfenum. 
2.  Of  the  brain,  and  nervous  medulla.  3.  A nerve.  4.  A 
mufcular  fibre.  5.  The  immediate  organs  of  fenfe.  6.  The 
external  organs  of  Jenfe.  7.  An  idea  or  fenfual  motion. 
8.  Perception.  9.  Scnfation.  10.  Rccollcftion  and Jug- 
gejiion.  11.  Habit,  caujation,  afifociation,  catenation.  12. 
Ref  ex  ideas.  13:  Stimulus  defined. 


As  fome  explanations  and  definitions  will  be  necefTary  in  the  profccutlon  of  the 
work,  the  reader  is  troubled  with  them  in  this  place,  and  is  intreated  to  keep 
them  in  his  mind  as  he  proceeds,  and  to  take  them  for  granted,  till  an  apt 
opportunity  occurs  to  evince  their  truth ; to  which  I lhall  premife  a very  fliort 
outline  of  the  animal  economy. 


I. — I.  THE  nervous  fyftem  has  its  origin  from  tire  brain, 
and  is  diftributed  to  every  part  of  die  body.  Thofe  nerves, 
which  ferve  the  fenfes,  principally  arife  from  that  part  of  the 
bram,  which  is  lodged  in  the  head ; and  thofe,  which  ferve  the 
purpofes  of  mufcular  motion,  principally  arife  from  diat  part 

«?f 


Sect.II.  i.  DEFINITIONS.  5 

of  the  brain,  which  is  lodged  in  tire  neck  and  back,  and  which  is 
erroneoufly  called  the  fpinal  marrow.  The  ultimate  fibrils  of 
thefe  nerves  terminate  in  the  immediate  organs  of  fenfe  and 
mufcular  fibres,  and  if  a ligature  be  put  on  any  part  of  their 
pafifage  from  the  head  or  fpine,  all  motion  and  perception  ceafe 
in  the  parts  beneath  the  ligature. 

2 . The  longitudinal  mufcular  fibres  compofe  the  locomotive 
mufcles,  whofe  contradfions  move  the  bones  of  the  limbs  and 
trunk,  to  which  tlieir  extremities  are  attached.  The  annular 
or  fpiral  mufcular  fibres  compofe  the  vafcular  mufcles,  which 
conftitute  the  inteftinal  canal,  the  arteries,  veins,  glands,  and 
abferbent  veffels. 

3.  The  immediate  organs  of  fenfe,  as  the  retina  of  the  eye, 
probably  confift  of  moving  fibrils,  with  a power  of  contra  chon 
limilar  to  that  of  the  larger  mufcles  above  deferibed. 

4.  The  cellular  membrane  conlifts  of  cells,  which  refemble 
thofe  of  a fponge,  communicating  with  each  other,  and  ccn- 
nedting  together  all  die  other  parts  of  the  body. 

5.  The  arterial  fyftem  conlifts  of  the  aortal  and  die  pulmo- 
nary artery,  which  are  attended  through  their  wlioie  courfe 
with  their  correfpondent  veins.  The  pulmonary  a r eery  re- 
ceives die  blood  from  the  right  chamber  of  the  heart,  and  car- 
ries it  to  the  minute  extenlive  ramifications  of  the  lungs,  where 
it  is  expofed  to  the  action  of  the  air  on  a furface  equal  to  that 
of  the  whole  external  Ikin,  through  the  thin  moift  coats  of 
thofe  veffels,  which  are  fpread  on  the  air-cells,  which  conftitute 
die  minute  terminal  ramifications  of  die  wind-pipe.  Here  die 
blood  changes  its  colour  from  a dark  red  to  a bright  fcarlet. 
It  is  then  collected  by  the  branches  cf  tire  pulmonary  vein,  and 
conveyed  to  the  left  chamber  of  the  heart. 

6.  The  aorta  is  another  large  artery,  which  receives  the 
blood  from  the  left  chamber  of  the  heart,  after  it  has  been  thus 
aerated  in  the  lungs,  and  conveys  it  by  afeending  and  descending 
branches  to  every  other  part  of  the  fyftem : the  extremities  of 
this  artery  terminate  either  in  glands,  as  the  falivary  glands,  la- 
chrymal glands,  &c.  or  in  capillary  veflels,  which  are  probably 
lefs  involuted  glands ; in  thefe  fome  fluid,  as  faliva,  tears,  per- 
fpiration,  are  feparated  from  the  blood ; and  the  remainder  of  the 
blood  is  abforbed  or  drank  up  by  branches  of  viens  correfpon- 
dent to  the  branches  of  the  artery ; which  are  fumifhed  with 
valves  to  prevent  its  return;  and  is  thus  carried  back,  after 
having  again  changed  its  colour  to  a dark  red,  to  the  right 
chamber  of  the  heart.  The  circulation  of  the  bleed  in  the  liver 
differs  from  this  general  fyftem ; for  the  veins  which  drink  up 
the  refluent  blood  from  thofe  arteries,  which  arc  fpread  on  the 

' . . bowels 


<3  DEFINITIONS.  Sect.  II.  2. 

bowels  and  mefentery,  unite  into  a trunk  in  the  liver,  and  fern; 
a kind  of  artery,  which  is  branched  into  the  whole  fubftance 
of  the  liver,  and  is  called  the  vena  portarum;  and  from  which 
the  bile  is  feparated  by  die  numerous  hepatic  glands,  which 
conftitute  that  vifeus. 

7.  The  glands  may  be  divided  into  three  fy items,  die  con- 
voluted glands,  fuch  as  tliofe  above  deferibed,  which  feparare 
bile,  tears,  faliva,  See.  Secondly,  the  glands  without  convo- 
lution, as  the  capillary  vellels,  which  unite  the  terminations 
of  the  arteries  and  veins,  and  feparate  both  the  mucus,  which 
lubricates  the  cellular  membrane,  and  the  peripirable  mart': 
which  preferves  the  (kin  moift  and  flexible,  A. id  diirdly,  the 
whole  abforbent  fyftem,  confiding  of  the  la&eals,  which  open 
their  mouths  in  the  ftomach  and  inteftines,  and  of  the  lym- 
phatics, which  open  their  mouths  on  the  external  iurface  of 
the  body,  and  on  the  internal  linings  of  the  ceils  of  the  cellular 
membrane,  and  other  cavities  of  the  body. 

Thefe  lacteal  and  lymphatic  veil'd  s are  furniflied  tilth  nu- 
merous valves  to  prevent  the  return  of  the  fluids,  which  they 
abforb,  and  terminate  in  glands,  called  lymphatic  glands,  and 
may  hence  be  ccnftdered  as  long  necks  or  mouths  belonging 
to  thefe  glands.  To  thefe  they  convey  the  chyle  and  mucus, 
with  a part  of  the  perfpirable  matter,  and  atmofpheric  nioifture : 
all  which,  after  having  puffed  through  tliefe  glands,  and  having 
fuffered  fome  change  in  them,  are  carried  forward  into  the 
blood,  and  fupply  perpetual  ncurifhment  to  the  fyftem,  or  re- 
place its  hourly  wade. 

8.  The  ftomach  and  inteftinal  canal  have  a conftant  vermi- 
cular motion,  which  carries  forward  their  contents,  after  the 
ladleals  have  drank  up  the  chyle  from  them;  and  which  is  ex- 
cited into  adbion  by  the  ftimulus  of  the  aliment  we  fwallow,  but 
which  becomes  oceaftonally  inverted  or  retrograde,  as  in  vomit- 
ing, and  in  the  iliac  paflion. 

11.  1.  The  word  jcnforium  in  the  following  pages  is  deflgned 
to  exnrefs  not  only  the  medullary  part  of  the  brain,  fpinal  marr 
row,  nerves,  organs  of  fenfe,  and  of  die  mufcles;  but  alfo  at 
the  fame  time  that  living  principle,  or  fpirit  ofanimation,  which 
relides  throughout  the  body,  without  being  cognizable  to  our 
fenfes,  except  by  its  exFefts.  The  changes  which  oceaftonally 
take  place  in  the  fenforium,  as  during  die  exertions  of  volition, 
or  the  fenfations  of  pleafure  or  pain,  are  termed  fenforial  na- 
tions. 

2.  Thefimilarity  of  the  texture  of  the  brain  to  diat  of  the 
pancreas,  and  fome  other  glands  of  the  bodv,  has  induced  the 
inquirers  into  this  fubjedl  to  believe,  that  a fluid,  perhaps  muc.i 

more 


DEFINITIONS. 


Sect.  II.  2. 


more  fubtile  than  the  eteCtric  aura,  is  feparated  from  the  blood 
by  that  organ  for  the  purpofes  of  motion  and  fenfation.  When 
we  recolleCt,  that  the  eleCtric  fluid  itfelf  is  actually  accumu- 
lated and  given  out  voluntarily  by  the  torpedo  and  tire  gyrnno- 
tus  eledtricus,  drat  an  eledfric  fhock  will  frequently  ftinrulate 
into  motion  a paralytic  limb,  and  laftly,  that  it  needs  no  per- 
ceptible tubes  to  convey  it,  this  opinion  feems  not  without  pro- 
bability; and  the  lingular  figure  of  the  brain  and  nervous  fyf- 
tem  feems  well  adapted  to  diftribute  it  over  every  part  of  the 

the  medullary  fubfcance  of  the  brain  not  only  occupies 
the  cavities  of  the  head  and  fpine,  but  pafles  along  the  innu- 
merable ramifications  of  the  nerves  to  the  various  mufcies  and 
organs  of  fenfe.  In  thefe  it  lays  afide  its  coverings,  and  is  in- 
termixed with  the  Fender  fibres,  which  ccnftitute  drofe  mufcies 
and  organs  of  fenfe.  Thus  all  thefe  diftairt  ramifications  of 
tire  fenforium  are  united  at  one  of  their  extremities,  that  is,  in 
the  head  and  fpine ; and  thus  thefe  central  parts  of  the  cenfoii- 
um  conftitute  a communication  between  all  the  organs  of  feme 
and  mufcies. 

3.  A nerve  is  a continuation  of  the  medullary  fubftance  of 
dre  brain  from  the  head  or  fpine  towards  the  other  parts  of  the 
body,  wrapped  in  its  proper  membrane. 

4.  The  mufcular  fibres  are  moving  organs  intermixed  'yvith 
drat  medullary  fubftance  which  is  continued  along  the  nerves, 
as  mentioned  above.  They  are  indued  with  the  power  of  con- 
traction, and  are  again  elongated  eidrer  by  antagonift  mufcies, 
by  circulating  fluids,  or  by  elaftic  ligaments.  So  dre  mufcies 
on  the  one  fide  of  the  fore-arm  bend  the  fingers  by  means  of 
their  tendons,  and  thofe  on  the  other  fide  of  the  fore-arm  ex- 
tend them  again.  The  arteries  are  diftended  by  the  circulating 
blood;  and  in  the  necks  of  quadrupeds  there  is  a ftrong  elaftic 
ligament,  which  afiifts  the  mufcies,  which  elevate  the  head, 
to  keep  it  in  its  horizontal  pofition,  and  to  raife  it  after  it  has 
been  deprefied. 

5.  The  immediate  organs  of  fenfe  confifc  in  like  manner  of 
moving  fibres  enveloped  in  the  medullary  fubftance  above  men- 
tioned; and  are  erroneoufly  fuppofed  to  be  fimply  an  ex  cm,  li- 
on of  the  nervous  medulla,  as  dre  retina  of  the  eye,  and  dre 
rete  mucofunr  of  the  {kin,  which  are  the  immediate  organs  of 
vifion,  and  of  touch.  Hence,  when  we  fpeak  of  the  contrac- 
tions of  the  fibrous  parts  of  the  body,  we  fhall  mean  both  die 
contractions  of  the  mufcies,  and  thofe  of  the  immediate  organs 
of  fenfe.  Tlrefe  fibrous  motions  are  thus  diftinguiflred  from 
the  fieri forial  motions  above  mentioned. 


6.  The 


8 


DEFINITIONS. 


Sect.  II.  2, 

6.  The  external  organs  of  fenfe  are  the  coverings  of  the 
immediate  organs  of  fenfe,  and  are  mechanically  adapted  for 
the*  reception  or  tranfmiffion  of  peculiar  bodies,  or  of  their 
qualities,  as  the  cornea  and  humours  of  the  eye,  the  tympanum 
of  the  ear,  the  cuticle  of  the  fingers  and  tongue. 

7.  I he  word  idea  has  various  meanings  in  the  writers  of 
metaphyfic : it  is  here  uled  limply  for  thofe  notions  of  external 
things,  which  our  organs  of  fenfe  bring  us  acquainted  with 
originally;  and  is  denned  a contraction,  or  motion,  or  con- 
figuration, oi  the  fibres,  which  conftitute  die  immediate  or- 
gan of  fenfe ; which  will  be  explained  at  large  in  anodier  part 
of  the  work.  Synonymous  with  the  word  idea,  we  (hall  iome- 
times  ufe  the  words  fenfual  motion,  in  contradiftindtion  to  muf- 
cular  motion. 

8.  The  word  perception  includes  both  the  adtion  of  the  or- 
gan of  fenfe  in  confequence  of  die  impadt  of  external  objects, 
and  our  attention  to  that  adtion ; that  is,  it  expreffes  both  die 
motion  of  the  organ  of  fenfe,  or  idea,  and  the  pain  or  pleafure 
that  iucceeds  or  accompanies  it. 

9.  The  pleafure  or  pain  which  neceffarily  accompanies  all 
thofe  perceptions  or  ideas  which  we  attend  to,  either  gradually 
iubiides,  or  is  fucceeded  by  other  fibrous  motions.  In  the  lat- 
ter cafe  it  is  termed  fenfation,  as  explained  in  Sedt.  V.  2,  and 
AT.-  2. — The  reader  is  intreated  to  keep  diis  in  his  mind,  that 
through  all  this  treatife  die  word  fenfation  is  ufed  to  exprels 
pleafure  or  pain  only  in  its  adtive  Hate,  by  whatever  means  it 
is  introduced  into  die  fyftem,  without  any  reference  to  the  fli- 
mulation  of  external  objects. 

10.  The  vulgar  ufe  of  the  word  memory  is  too  unlimited 
for  our  purpofe : thole  ideas  which  we  voluntarily  recall  are 
here  termed  ideas  of  recolledhon,  as  when  we  will  to  repeat 
the  alphabet  backwards.  And  thofe  ideas  which  are  fuggefted 
to  us  by  preceding  ideas,  are  here  termed  ideas  of  fuggeftion,  as 
whilfl:  we  repeat  die  alphabet  in  the  ufual  order;  when  by- 
habits  previoully  acquired  B is  fuggefted  by  A,  and  C by  B, 
without  any  effort  of  deliberation. 

1 1.  The  word  affociation  properly  fignifies  a fociety  or  con- 
vention of  things  in  fome  reipedts  iimilar  to  each  odier.  We 
never  fay  in  common  language,  that  the  effect  is  affociatcd 
with  the  caufe,  though  they  nteeffariiy  accompany  or  lucceed 
each  other.  Thus  die  contractions  or  our  mufcles  and  organs 
of  fenfe  may  be  laid  to  be  affociated  with  irritations,  or  with 
volition,  or  with  fenfation ; becaufe  they  are  caufed  bv  them, 
as  mentioned  in  Sedt.  IV.  When  fibrous  contradtions  fuc- 
cced  other  fibrous  contradtions,  the  conacdtion  is  termed  affo- 


Sect.  III.  MOTIONS  OF  THE  RETINA. 


9 

elation  ; when  fibrous  contractions  fucceed  fenforial  motions, 
the  connection  is  termed  caufation ; when  fibrous  and  fenforial 
motions  reciprocally  introduce  each  other  in  progreffive  trains 
or  tribes,  it  is  termed  catenation  of  animal  motions.  All  thefe 
connections  are  faid  to  be  produced  by  habit ; that  is,  by  fre- 
quent repetition. 

12.  It  may  be  proper  to  obferve,  that  by  the  unavoidable 
idiom  of  our  language  the  ideas  of  perception,  of  recolleCtion, 
or  of  imagination,  in  the  plural  number  fignify  the  ideas  be- 
longing to  perception,  to  recolleCtion,  or  to  imagination; 
whiilt  the  idea  of  perception,  of  recolleCtion,  or  of  imagina- 
tion, in  the  lingular  number  is  ufed  for  what  is  termed  “ a re- 
flex idea  of  any  of  thofe  operations  of  the  fenforium.” 

13.  By  the  word  Jlimulus  is  not  only  meant  the  application 
of  external  bodies  to  our  organs  of  lenfe  and  mufcular  fibres, 
which  excites  into  aCtion  the  fenforial  power  termed  irritation ; 
but  alio  pleafure  or  pain,  when  they  excite  into  aCtion  the  fen- 
forial power  termed  lenfation;  and  defire  or  averflon,  when 
they  excite  into  aCtion  the  power  of  volition ; and  laftly,  the 
fibrous  contractions  which  precede  affociation;  as  is  further 
explained  in  SeCt.  XII.  2.  1. 

SECT.  III. 

THE  MOTIONS  OF  THE  RETINA  -DEMONSTRATED 
BY  EXPERIMENTS. 

I.  Of  animal  motions  and  of  ideas.  II.  The  fibrous  Jlrudiure 
of  the  retina.  III.  The  adiivlty  of  the  retina  in  vifion.  1. 
Rays  of  light  have  no  momentum.  2.  Objects  long  viewed 
become  fainter . 3.  Spedira  of  black  objects  become  lumi- 
nous. 4.  Varying  fpe  dir  a from  gyration.  5.  From  long  in - 
fpedtion  of  various  colours.  IV.  Motions  of  the  organs 
of  fenfe  confiitute  ideas.  1.  Light  from  prejfing  the  eye- 
ball, and  jound from  the  pulfation  of  the  caroted  artery. 
2.  Ideas  in  fieep  miftaken  for  perceptions.  3.  Ideas  of  ima- 
gination produce  pain  and  ficknefs  like  fenfations.  4. 
IVhen  the  organ  of  fenje  is  defrayed , the  ideas  belonging 
to  that  Jenfe perijh.  V.  Analogy  between  mufcular  motions 
and  fenjual  motions,  or  ideas.  1.  They  are  both  originally 
excited  by  irritations.  2.  And  affociatcd  together  in  the 
fame  manner.  3.  Both  adi  in  nearly  the  fame  times.  4.  Are 
alike  firengthened  or  fatigued  by  exerclfe.  5.  Are  alike 
painful from  inflammation.  6.  Are  alike  benumbed  by  com - 
C prejfon . 


xo  MOTIONS  OF  THE  RETINA.  Sect. III.  i, 

preffon.  7.  Are  alike  liable  to  paralyjis.  8.  To  convulfion . 
9.  To  the  influence  of  old  age.  VI.  Objections  anfwered. 
X.  Why  we  cannot  invent  new  ideas.  2.  If  ideas  referable 
external'objeCts.  3.  Of  the  imagined  fenfation  in  an  am- 
putated limb.  4.  AbfiraCt  ideas.  VII.  What  are  ideas , 
if  they  are  not  animal  motions. 

BEFORE  the  great  variety  of  animal  motions  can  be  duly 
arranged  into  natural  claffes  and  orders,  it  is  neceffary  to  fmooth 
the  way  to  this  yet  unconquered  field  of  fcience,  by  removing 
fome  obftacles  which  thwart  our  paffage.  I.  To  demonflratc 
that  the  retina  and  other  immediate  organs  of  fenfe  poffefs  a 
power  of  motion,  and  that  thefe  motions  conftitute  our  ideas, 
according  to  the  fifth  and  feventh  of  the  preceding  affertions, 
claims  our  firfl  attention. 

Animal  motions  are  diftinguifhed  from  the  communicated 
motions,  mentioned  in  the  firft  fedlion,  as  they  have  no  mecha- 
nical proportion  to  their  caufe ; for  the  goad  of  a fpur  on  the 
fkin  of  a horfe  fhall  induce  him  to  move  a load  of  hay.  They 
differ  from  the  gravitating  motions  there  mentioned,  as  they  are 
exerted  with  equal  facility  in  all  directions ; and  they  differ 
from  the  chemical  clafs  of  motions,  becaufe  no  apparent  de- 
compofitions  or  new  combinations  are  produced  in  the  moving 
materials. 

Hence,  when  we  fay  animal  motion  is  excited  by  irritation, 
we  do  not  mean  that  the  motion  bears  any  proportion  to  the 
mechanical  impulfe  of  the  flimulus ; nor  that  it  is  affedled  by 
the  general  gravitation  of  the  two  bodies ; nor  by  their  chemical 
properties ; hut  foiely,  that  certain  animal  fibres  are  excited  into 
adlion  by  fomething  external  to  the  moving  organ. 

In  this  fenfe  the  flimulus  of  the  blood  produces  the  contrac- 
tions of  the  heart ; and  the  fubflances  we  take  into  our  ftomach 
and  bowels  irritate  them  to  perform  their  neceffarv  functions. 
The  rays  of  light  excite  the  retina  into  animal  motion  by  their 
flimulus ; at  the  fame  time  that  thofe  rays  of  light  themfelves 
are  phyfically  converged  to  a focus  by  the  inactive  humours  of 
the  eve.  Tire  vibrations  of  the  air  irritate  the  auditory  nerve 
into  animal  adlion;  while  it  is  probable  that  the  tympanum  of 
the  ear  at  the  fame  time  undergoes  a mechanical  vibration. 

To  render  this  tire  um  fiance  more  eafy  to  be  comprehended. 
motion  may  be  defined  to  be  a variation  cf  figure ; for  the 
whole  univerfe  may  be  confidered  as  one  thing  poffeffing  a cer- 
tain figure;  the  motions  of  any  of  its  parts  are  a variation  of 
this  figure  of  the  whole  : this  definition  of  motion  will  he  fur- 
ther explained  in  Sect.  XiV.  2.  2.  on  the  production  of  ideas. 

Now, 


£ . <■ 

. - ' : ' 

i.'-  V : 


*•  . 


V 


II 


Sect.  III.  i.  MOTIONS  OF  THE  RETINA. 

Now,  the  motions  of  an  organ  of  fenfe  are  a fucceflion  of 
configurations  of  that  organ  ; thefe  configurations  fucceed  each 
other  quicker  or  flower ; and  whatever  configuration  of  this 
organ  of  fenfe,  that  is,  whatever  portion  of  the  motion  of  it  is, 
or  has  ufuallv  been,  attended  to,  conftitutes  an  idea.  Hence 
the  configuration  is  not  to  be  confidered  as  an  effect  of  the  mo- 
tion of  the  organ,  but  rather  as  a part  or  temporary  termination 
of  it;  and  that,  whether  a paufe  fucceeds  it,  or  a new  configu- 
ration immediately  takes  place.  . Thus,  when  a fucceflion  of 
moving  objects  are  prefented  to  our  view,  the  ideas  of  trumpets, 
horns,  lords  and  ladies,  trains  and  canopies,  are  configurations, 
that  is,  parts  or  links  of  the  fucceflive  motions  of  the  organ 
of  vifion. 

Thefe  motions,  or  configurations  of  the  organs  of  fenfe, 
differ  from  the  fenforial  motions  to  be  defcribed  hereafter,  as 
they  appear  to  be  Amply  contractions  of  the  flbrous  extremi- 
ties of  thofe  organs,  and  in  that  refpect  exactly  referable  the 
motions  or  contractions  of  the  larger  mufcles,  as  appears  from 
the  following  experiment  :■ — Place  a circular  piece  of  red  Aik, 
about  an  inch  in  diameter,  on  a flieet  of  white  paper,  in  a Arong 
light,  as  in  Plate  I.- — look  for  a minute  on  thi^area,  or  till  the 
eye  becomes  fomewnat  fatigued,  and  then,  gently  cloAng  your 
eyes,  and  {hading  them  with  your  hand,  a circular  green  area 
of  die  fame  apparent  diameter  becomes  viAble  in  the  clofed  eye. 
This  green  area  is  the  colour  reverie  to  the  red  area,  which  had 
been  previoufly  infpected,  as  explained  in  experiments  on  ocu- 
lar fpectra  at  the  end  of  the  work,  and  in  Botanical  Garden, 
P.  I.  additional  note,  No.  I.  Hence  it  appears,  that  a part  of 
me  retina,  which  had  been  fatigued  by  contraction  in  one  di- 
rection, relieves  itfelf  by  exerting  the  antagonifl:  Abres,  and  pro- 
ducing a contraction  in  an  oppoAte  direction,  as  is  common  in 
the  exertions  of  our  mufcles.  .Thus,  when  we  are  tired  with 
long  action  of  our  arms  in  one  direction,  as  in  holding  a bridle 
on  a journey,  we  occaAonally  throw  them  into  an  oppoAte 
poAtion  to  relieve  the  fatigued  mufcles. 

Mr.  Locke  has  dehned  an  idea  to  be  “ whatever  is  prefent 
to  the  mind;”  but  this  would  include  the  exertions  of  volition, 
and  the  fenfations  of  pleafure  and  pain,  as  well  as  thofe  opera- 
tions of  our  fyAem,  which  acquaint  us  with  external  objects  ; 
and  is  therefore  too  unlimited  for  our  purpofe.  Mr.  Locke  feems 
to  have  fallen  into  a further  error,  by  conceiving  that  the  mind 
could  form  a general  or  abftract  idea  by  its  own  operation, 
which  was  the  copy  of  no  particular  perception ; as  of  a triangle 
in  general,  that  was  neither  acute,  obtufe,  nor  right  angled. 
The  ingenious  Dr.  Berkley  and  Mr.  Hume  have  demonftrated, 

that 


12  MOTIONS  OF  THE  RETINA.  Sect.  III.  2.  3. 

that  fuch  general  ideas  have  no  exiftence  in  nature,  not  even 
In  the  mind  of  their  celebrated  inventor.  We  fhall  therefore 
take  for  granted  at  prefent,  that  our  recollection  or  imagination 
of  external  objects  conlifts  of  a partial  repetition  of  the  percep- 
tions which  were  excited  by  thofe  external  objects  at  the  time 
we  became  acquainted  with  them;  and  that  our  reflex  ideas  of 
the  operations  of  our  minds  are  partial  repetitions  of  thofe 
operations. 

II.  The  following  article  evinces  that  the  organ  of  vifion 
confifts  of  a fibrous  part  as  w7ell  as  of  the  nervous  medulla, 
like  other  white  mufcles ; and  hence,  as  it  refembles  the  mufeu- 
lar  parts  of  the  body  in  its  ftruclure,  we  may  conclude,  that  it 
muft  refemble  them  in  pofTefling  a power  of  being  excited  into 
animal  motion. — The  fubfequent  experiments  on  the  optic 
nerve,  and  on  the  colours  remaining  in  the  eye,  are  copied  from 
a paper  on  ocular  fpedxa,  publifhed  in  the  76th  volume  of  the 
Philof.  Tranf.  by  Dr.  R.  Darwin  of  Shrewfbury,  which,  as  I 
ihall  have  frequent  occafion  to  refer  to,  is  reprinted  in  this 
work,  Seci.  XL.  The  retina  of  an  ox’s  eye  was  fufpended  in 
a glafs  of  warm  water,  and  forcibly  torn  in  a few  places  ; the 
edges  of  drefe  pa/ts  appeared  jagged  and  hairy,  and  did  not  con- 
tract and  become  fmooth  like  Ample  mucus,  when  it  is  diftended 
till  it  breaks,  which  evinced  that  it  conlifted  of  fibres.  This 
fibrous  conftru&ion  became  ftill  more  diftinCt  to  the  light  by 
adding  fome  cauftic  alkali  to  the  water;  as  the  adhering  mucus 
was  firft  eroded,  and  the  hair-like  fibres  remained  floating  in 
theveflel.  Nor  does  the  degree  of  tranfparency  of  the  retina 
Invalidate  this  evidence  of  its  fibrous  ftruCture,  fince  Leeuwen- 
hoek has  fhewn,  that  the  chryftaline  humour  itfelf  confifts  of 
fibres.  Arc.  Nat.  V.  I.  70. 

Hence  it  appears,  that  as  the  mufcles  confift  of  larger  fibres, 
Intermixed  with  a fmaller  quantity  of  nervous  medulla,  the 
organ  of  vifion  conlifts  of  a greater  quantity  of  nervous  medul- 
la, intermixed  with  fmaller  fibres.  It  is  probable  that  the  loco- 
motive mufcles  of  microfcopic  animals  may  have  greater  tenuity 
than  thofe  of  the  retina  ; and  there  is  reafon  to  conclude,  from 
analogy,  that  the  other  immediate  organs  of  fenfe,  as  the  portio 
mollis  of  the  auditory  merve,  and  the  rete  mucofum  of  the  fkin, 
poflefs  a iimilarity  of  ftruCture  with  the  retina,  and  a fimilar 
power  of  being  excited  into  animal  motion. 

III.  The  fubfequent  articles  fhew,  that  neither  mechanical 
impreiiions,  nor  chemical  combinations  of  light,  but  that  the 
animal  activity  of  the  retina  conftitutes  vifion. 

1.  Much  has  been  conjectured,  by  philofophers,  about  the 
momentum  of  the  rays  of  light:  to  fubjeCt  this  to  experiment, 

a verv 


. 

. < ’ ■ 

' 

< 


Sect.  III.  3.  MOTIONS  OF  THE  RETINA.  13 

a very  light  horizontal  balance  was  conftructed  by  Mr.  Michel, 
with  "about  an  inch  fquare  of  thin  leaf-copper  fufpended  at  each 
end  of  it,  as  defcribed  in  Dr.  Pfieftley’s  Hiftory  of  Light  and 
Colours.  The  focus  of  a very  large  convex  mirror  was  thrown 
by  Dr.  Powel,  in  his  leisures  on  experimental  philofophy,  in 
my  prefence,  on  one  wing  of  this  delicate  balance,  and  it  re- 
ceded from  the  light;  thrown  on  the  other  wing,  it  approached 
towards  the, light,  and  this  repeatedly;  fo  that  no  fenfible  im- 
pulfe  could  be  obferved,  but  what  might  well  be  afcribed  to  the 
afcent  of  heated  air. 

Whence  it  is  reafonable  to  conclude,  that  the  light  of  the 
day  muft  be  much  too  weak,  in  its  dilute  Hate,  to  make  any 
mechanical  imprefiion  on  fo  tenacious  a fubftance  as  the  retina 
of  the  eye. — Add  to  this,  that  as  the  retina  is  nearly  tranfpa- 
rent,  It  could  therefore  make  lefs  refiftance  to  the  mechanical 
impulfe  of  light ; which,  according  to  the  obfervations  related 
by  Mr.  Melvil,  in  the  Edinburgh  Literary  Eflays,  only  com- 
municates heat,  and  fhould  therefore  only  communicate  mo- 
mentum, where  it  is  obftrudled,  refle&ed,  or  refratfled. — ■ 
From  whence  alfo  may  be  collected  the  final  caufe  of  this  de- 
gree of  tranfparency  of  the  retina,  viz.  leaft  by  the  focus  of 
flronger  lights,  heat  and  pain  fhould  have  been  produced  in 
the  retina,  inftead  of  that  ftimulus  which  excites  it  into  ani- 
mal motion. 

2.  On  looking  long  On  an  area  of  fcarlet  filk  of  about  an 
inch  in  diameter  laid  on  white  paper,  as  in  Plate  I.  the  fcarlet 
Colour  becomes  fainter,  till  at  length  it  entirely  vanifhes„ 
though  the  eye  is  kept  uniformly  and  fteadily  upon  it.  Now, 
if  the  change  or  motion  of  the  retina  Was  a mechanical  im- 
preffion,  or  a chemical  tinge  of  coloured  light,  the  perception 
would  every  minute  become  flronger  and  flronger, — -whereas 
ih  this  experiment  it  becomes  every  inftant  weaker  and  weaker. 
The  fame  circumftance  obtains  in  the  continued  application 
of  found,  or  of  fapid  bodies,  or  of  odorous  ones,  or  of  tangi- 
ble ones,  to  their  adapted  organs  of  fenfe. 

Thus,  when  a circular  coin,  as  a {hilling,  is  prefled  on  the 
palm  of  the  hand,  the  fenfe  of  touch  is  mechanically  com- 
prefled ; but  it  is  the  flimulus  of  this  preflure  that  excites  the 
organ  of  touch  into  animal  adbion,  which  conftkutes  the  per- 
ception of  hardnefs  and  of  figure:  for  in  fome  minutes  the 
perception  ceafes,  though  the  mechanical  preflure  of  the  ob- 
ject remains. 

3.  Make  with  ink  on  white  paper  a very  black  fpot  about 
half  an  inch  in  diameter,  with  a tail  about  an  inch  in  length, 
io  as  to  refemble  a tadpole,  as  in  Plate  II.;  lcck  ftecflaftly 

D for 


i4  MOTIONS  OF  THE  RETINA.  Sect.  III.  3. 

for  a minute  on  the  center  of  this  fpot,  and  on  moving  the  eve 
a little,  the  figure  of  the  tadpole  will  be  feen  on  the  white 
part  of  the  paper ; which  figure  of  the  tadpole  will  appear 
more  luminous  than  the  other  part  of  the  white  paper;  which 
can  only  be  explained  by  fuppofing  that  part  of  the  retina, 
on,  which  the  tadpole  was  delineated,  to  have  become  more 
fenfible  to  light  than  the  other  parts  of  it,  which  were  expof- 
ed  to  the  white  paper;  and  not  from  anv  idea  of  mechanical 
imprefhon  or  chemical  combination  of  light  with  the  retina. 

4.  When  any  one  turns  round  rapidly,  till  he  becomes  diz- 
zy, and  falls  upon  the  ground,  the  lpedra  of  the  ambient  ob- 
jedls  continue  to  prefent  themfelves  in  rotation,  and  he  feeins 
to  behold  the  objects  ftill  in  motion.  Now  if  thefe  fpedtra 
were  impreiTions  on  a paftive  organ,  they  either  muft  conti- 
nue as  they  were  received  laft,  or  not  continue  at  all. 

5.  Place  a piece  of  red  filk,  about  an  inch  in  diameter,  on  a 
Iheet  of  white  paper,  in  a ftrong  light,  as  in  Hate  I. ; look  ftea- 
dily  upon  it,  from  the  diftance  of  about  half  a yard,  for  a minute ; 
then  doling  your  eye-lids,  cover  them  with  your  hands  and 
handkerchief,  and  a green  fpedtrum  will  be  feen  in  your  eves, 
relembling,  in  form,  the  piece  of  red  lilk.  After  fome  feconds 
of  time  the  fpectrum  will  difappear,  and  in  a few  more  feconds 
will  re-appear ; and  thus  alternately  three  or  fcJur  times,  if  the 
experiment  be  well  made,  till  at  length  it  vanishes  entirely. 

6.  Place  a circular  piece  of  white  paper,  about  four  inches 
in  diameter,  in  the  funfhine ; cover  the  center  of  this  with  a 
circular  piece  of  black  iilk,  about  three  inches  in  diameter ; 
and  the  center  of  the  black  lilk  with  a circle  of  pink  filk, 
about  two  inches  in  diameter;  and  the  center  of  the  pink  filk 
with  a circle  of  yellow  lilk,  about  one  inch  in  diameter;  and 
the  center  of  this  with  a circle  of  blue  filk,  about  half  an  inch 
in  diameter ; make  a linall  fpot  with  ink  in  the  center  of  the 
blue  lilk,  as  in  Plate  III. ; look  fteadily  for  a minute  on  this 
central  fpot,  and  then  doling  your  eyes,  and  applying  your  hand 
at  about  an  inch  diflance  before  them,  fo  as  to  prevent  too 
much  or  too  little  light  from  palling  through  the  eve-lids,  and 
you  will  fee  the  mold  beautiful  circles  ot  colours  that  imagina- 
tion can  conceive ; \Vhich  are  moll  refembled  by  the  colours 
occalioned  by  pouring  a drop  or  two  of  oil  on  a ftill  take 
in  a bright  day.  But  thefe  circular  irifes  of  colours  are  not 
only  different  from  the  colours  of  the  filks  above-mentioned, 
but  are  at  the  fame  time  perpetually  changing  as  long  as  they 
exift. 

From  all  thefe  experiments  it  appears,  that  thefe  fpedra  in 
the  eye  are  not  owing  to  the  mechanical  impulfe  of  light  im- 

prelTcd. 


* 


•1 


* 


* 


% 


\ 


Sect. ill.  4-  MOTIONS  OF  THE  RETINA.  15 

preffed  on  the  retina ; nor  to  its  chemical  combination  with 
that  organ ; nor  to  the  abforption  and  emiflion  of  light,  as  is 
fuppofed,  perhaps  erroneoufly,  to  take  place  in  calcined  {hells 
and  other  phofphorefcent  bodies,  after  having  been  expofed  to 
the  light : for  in  all  thefe  cafes  the  lpeclra  in  the  eye  {honld  ei- 
ther remain  of  the  fame  colour,  or  gradually  decay,  when  the 
object  is  withdraw ; and  neither  their  evanefcence  during  the 
prefence  of  their  objedl,  as  in  the  fecond  experiment,  nor  their 
change  from  dark  to  luminous,  as  in  the  third  experiment, 
nor  their  rotation,  as  in  the  fourth  experiment,  nor  the  alternate 
prefence  and  evanefcence  of  them,  as  in  the  fifth  experiment, 
nor  the  perpetual  change  of  colours  of  them,  as  in  the  lafl 
experiment,  pould  exifl. 

IV.  The  fubfequent  articles  fhew,  that  thefe  animal  motions, 
or  configurations  of  our  organs  of  fenfe,  conftitute  our  ideas. 

1 . If  any  one  in  the  dark  preffes  the  ball  of  his  eye,  by  ap- 
plying his  finger  to  the  external  corner  of  it,  a luminous  ap- 
pearance is  obferved ; and  by  a fmall  flroke  on  the  eye  great 
flafhes  of  fire  are  perceived.  (Newton’s  Optics.)  So  that, 
when  the  arteries,  that  are  near  the  auditory  nerve,  make 
ftronger  pulfations  than  ufual,  as  in  fome  fevers,  an  undulating 
found  is  excited  in  the  ears.  Hence  it  is  not  the  prefence  of 
the  light  and  found,  but  the  motions  of  the  organ,  that  are 
immediately  neceffary  to  conftitute  the  perception  or  idea  of 
light  and  found. 

2.  During  the  time  of  deep,  or  in  delirium,  the  ideas  of 
imagination  are  miftaken  for  the  perceptions  of  external  ob- 
jects ; whence  it  appears,  that  thefe  ideas  of  imagination  are  no 
other  than  a reiteration  of  thofe  motions  of  the  organs  of  fenfe, 
which  were  originally  excited  by  th<=  ftimulus  of  external  ob- 
jedfs  : and  in  our  waking  hours  the  fimple  ideas,  that  we  call 
up  by  recolledfion  or  by  imagination,  as  the  colour  of  red, 
or  the  fmell  of  a rofe,  are  exadf  refemblances  of  the  fame 
fimple  ideas  from  perception ; and  in  confequence  mu  ft  be  a 
repetition  of  thofe  very  motions. 

3.  The  difagreeable  fenfation  called  the  tooth-edge  is  origi- 
nally excited  by  the  painful  jarring  of  the  teeth  in  biting  the 
edge  of  the  glafs,  or  porcelain  cup,  in  which  our  food  was 
given  us  in  our  infancy,  as  is  further  explained  in  the  Section 
XVI.  10,  on  Inftindt. — This  difagreeable  fenfation  is  after- 
wards excitable  not  only  by  a repetition  of  the  found,  that 
was  then  produced,  but  by  imagination  alone,  as  I have  my- 
felf  frequently  experienced ; in  this  cafe  the  idea  of  biting  a 
china  cup,  when  1 imagine  it  very  diftindfly,  or  when  I fee 
another  perfon  bite  a cup  or  glafs,  excites,  an  aclual  pain  in 

the 


*6  '"MOTIONS  OF  THE  RETINA.  Sect.  Ill  4, 

the  nerves  of  mv  teeh.  So  that  this  idea  and  pain  feem  to  be 
-nothing  more  than  the  reiterated  motions  of  thofe  nerves,  that 
were  formerly  fo  difagreeably  affected . 

Other  ideas  that  are  excited  by  imagination  or  recollection 
in  many  infiances  produce  firailar  effects  on  the  conftitution, 
as  our  perceptions  had  formerly  produced,  and  are  therefore 
undoubtedly  a repetition  of  the  fame  motions.  A fforv  which 
the  celebrated  Baron  Van  Swietop  relates  of  himfelf  is  to  this 
purpofe.  He  was  prefent  when  the  putrid  carcafe  of  a dead 
dog  exploded  with  prodigious  Bench;  and  fo  me  rears  after- 
wards, accidentally  riding  along  the  fame  road,  he  was  thrown 
mto  tire  fame  ficknefs  and  vomiting  by  the  idea  of  tips  Bench, 
as  he  had  before  experienced  from  the  perception  of  it. 

4.  Vvrhere  the  organ  of  fenfe  is  totally  dcBroved,  the  ideas 
which  were  received  by  that  organ  feem  to  perilh  along  with 
it,  as  wejl  as  the  power  of  perception.  Of  this  a fatisfackorv 
mftance  has  fallen  under  my  .obfervation.  A gentleman  about 
fixty  years  of  age  had  been  totally  deaf  for  near  thirty  years  ; 
he  appeared  to  be  a man  of  good  underllanding,  and  amufed 
himfelf  with  reading,  and  by  converfing  either  bv  the  ufe  of 
the  pen,  or  by  figns  rpide  with  his  fingers,  to  reprefent  letters. 
I obferved  that  he  had  fo  far  forgot  the  pronunciation  of  the 
language,  that  when  he  attempted  to  fpeak,  none  of  his  words 
had  difiindk  articulation,  though  his  relations  could  fometimes 
underhand  his  meaning.  But,  which  is  much  to  the  point, 
he  allured  me,  that  in  his  dreams  he  always  imagined  that  peo- 
ple converfed  with  him  by  figns  or  writing,  and  never  that 
Ire  heard  any  one  fpeak  to  him.  From  hence  it  appears, 
that  with  the  perceptions  of  founds  Ire  Iris  alio  lofi  the  ideas 
of  them ; though  the  organs  of  fpeech  Bill  retain  fopnewhat  of 
their  ufual  habits  of  articulation. 

This  obfervation  may  throw  fome  light  on  the  medical  treat- 
ment of  deaf  people  ; as  it  may  be  learnt  from  their  dreams 
whether  tire  auditory  nerve  be  paralytic,  or  their  deafnefs  be 
owing  to  fome  defebi  of  the  external  organ. 

Jt  rarely  happens  that  the  immediate  organ  of  vifion  is  per- 
fectly deffroved.  The  mofi  frequent  caufes  of  blindnefs  are 
occafioned  by  defects  of  the  external  organ,  as  in  cata  rafts 
and  obfufeations  of  the  cornea.  But  I have  had  the  opportu- 
nity of  converfing  with  two  men,  who  had  been  fome  years 
blind  ; one  of  them  had  a complete  gutta  ferena,  and  tire  other 
had  lofi  the  ivhole  fubfiance  of  his  eyes.  They  both  told  me 
that  they  did  not  remember  to  have  ever  dreamt  of  vilible  ob- 
jects, fince  the  total  lofs  of  their  fight. 

V,  Another  method  of  difeovering  that  our  ideas  are  ani- 
mal 


Sect.  III.  5.  MOTIONS  OF  THE  RETINA.  17 

mal  motions  of  the  organs  of  fenfe,  is  from  conlidering  the 
great  analogy  they  bear  to  the  motions  of  the  larger  mufcles 
of  the  body.  In  the  following  articles  it  will  appear  that  they 
arc  originally'  excited  into  adtion  by  the  irritation  of  external 
objects  like  our  mufcles  ; are  afibciated  together  like  curmuf- 
cular  motions ; act  in  fnnilar  time  with  them ; are' fatigued  by 
continual  exertion  like  them;  and  that  the  organs  of  fenfe  are 
fubject  to  inflammation,  numbnefs-,  palley,  convulfron,  and 
the  defedts  of  old  age,  in  the  fame  manner  as  the  mufcular 
fibres. 

1.  All  our  perceptions  or  ideas  of  external  objects  are  uni- 
verfally  allowed  to  have  been  originally  excited  by  the  ftimu- 
lus  of  thole  external  objedts  ; and  it  will  be  fhewn  in  a luc- 
ceeding  fedtion,  that  it  is  probable  that  all  our  mnfeular  mo- 
tions, as  well  thole  that  are  become  voluntary  as  thole  of  the 
heart  and  glandular  lyitem,  were  originally  in  like  manner 
excited  by  the  ftimulus  of  fomething  external  to  the  organ  of 
motion. 

2.  Our  ideas  are  alfo  affociated  together  after  their  produc- 
tion precifely  in  the  lame  manner  as  our  mulcular  motions , 
which  will  likewife  be  fully  explained  in  the  lucceeding  fecaon. 

3.  The  time  taken  up  in  performing  an  idea  is  likewife 
much  the  fame  as  that  taken  up  in  performing  a mufcular  mo- 
tion. A mufician  can  prefs  the  keys  of  an  harplichord  with 
his  fingers  in  the  order  of  a tune  he  has  been  aceuftomed  to 
play,  in  as  little  time  as  he  can  run  over'  thole  notes  in  his 
mind.  So  we  many  times  in  an  hour  cover  cur  eye-balls  with 
our  eye-lids  without  perceiving  that  we  are  in  the  dark ; hence 
the  perception  or  idea  of  light  is  not  changed  for  that  of  daik- 
nels  in  fa  fmall  a time  as  the  twinkling  of  an  eye ; fo  that  in. 
this  cafe  the  mufcular  motion  of  the  eye-lid  is  performed 
quicker  than  the  perception  of  light  can  be  changed  for  that 
of  darknefs. — So  if  a rire-ilick  be  whirled’ round  in  the  dark, 
a luminous  circle  appears  to  the  obferver;  if  it  be  whirled 
iomewhat  flower,  this  circle  becomes  interrupted  in  one  part 
and  then  the  time  taken -up  in  fucha  revolution  of  the  flick  is 
the  lame  that  the  obferver  ufes  in  changing  his  ideas : thus  the. 

oxo-  of  Homer,  the  long  ihadow  of  the  flying  ja- 
velin, is  elegantly  defigned  to  give  us  an  idea  of  its  velocity, 
and  nor  of  its  length. 

4.  I he  fatigue  that  follows  a continued,  attention  of  the 
mind  to-one  object  is  relieved  by  changing  the  iubjedt  of  our 
thoughts ; as  the  continued  movement  of  one  limb  is  relieved 
by  moving  another  in  its  head.  Whereas  a due  exercife  -of 
*he  faculties  cf  the  mind  llrengtfwns  and  improves  thole  facul- 
ties. 


18  MOTIONS  OF  THE  RETINA.  Sect.  III.  5; 

ties,  whether  of  imagination  or  recollection ; as  the  exercife 
of  our  limbs  in  dancing  or  fencing  increafes  the  ftrength  and 
agility  of  life  mufcles  thus  employed. 

5.  If  the  mufcles  of  any  limb  are  inflamed,  they  do  not 
move  without  pain ; fo  when  the  retina  is  inflamed,  its  mo- 
tions alfo  are  painful.  Hence  light  is  as  intolerable  in  this 
kind  of  ophthalmia,  as  the  preffure  is  to  the  Anger  in  the  pa- 
ronychia. In  this  difeafe  the  patients  frequently  dream  of 
having  their  eyes  painfully  dazzled ; hence  the  idea  of  ftrong 
light  is  painful  as  well  as  the  reality.  The  firfl  of  thefe  facts 
evinces  that  our  perceptions  are  motions  of  the  organs  of 
fenfe ; and  the  latter,  that  our  imaginations  are  alfo  motions  of 
the  fame  organs. 

6.  The  organs  of  fenfe,  like  the  moving  mufcles,  are  lia- 
ble to  become  benumbed,  or  lefs  fenfible,  from  compreffion. 
Thus,  if  any  perfort  on  a light  day  looks  on  a white  wall,  he 
may  perceive  the  ramifications  of  the  optic  artery,  at  every 
Sulfation  of  it,  reprefented  by  darker  branches  on  the  white 
wall ; which  is  evidently  owing  to  its  comprefling  the  retinue 
during  the  diaftole  of  the  artery.  Savage  Nofolog, 

7.  The  organs  of  fenfe  and  the  moving  mufcles  are  alike 
liable  to  be  afFedted  with  paify,  as  in  the  gutta  ferena,  and  in 
fome  cafes  of  deafnefs  ; and  one  fide  of  the  face  has  fometimes 
loft  its  power  of  fenfation,  but  retained  its  power  of  motion  ; 
other  parts  of  the  body  have  loft  their  motions,  but  retained 
their  fenfation,  as  in  the  common  hemiplagia ; and  in  other 
inftances  both  thefe  powers  have  perifhed  together. 

8.  In  fome  convulfive  difeafes  a delirium  or  infanity  fuper- 
venes,  and  theconvulftons  ceafe  ; and  converfelv  the  convul- 
flons  {hall  fup'ervene,  and  the  delirium  ceafe. — Of  this  I have 
been  a witnefs  many  times  in  a day  in  the  paroxyfms  of  violent 
epilepftes ; which  evinces  that  one  kind  of  delirium  is  a convul- 
fion  of  the  organs  of  fenfe,  and  that  our  ideas  are  the  motions 
of  thefe  organs : the  fubfequent  caies  will  illuftrate  this  ob- 
fervation. 

Mils  G , a fair  young  lady,  with  light  eyes  and  hair, 

was  ieized  with  moft  violent  convuliions  of  her  limbs,  with 
outrageous  hiccough,  and  moft  vehement  efforts  to  vomit : af- 
ter near  an  hour  was  elapfed  this  tragedy  ceaied,  and  a calm 
talkative  delirium  fupervened  for  about  another  hour ; and 
thefe  relieved  each  other  at  intervals  during  the  gieateft  part  of 
three  or  four  days.  After  having  carefully  coiiftdered  this 
difeafe,  I thought  the  convuliions  of  her  ideas  lefs  dangerous 
than  thofe  of  her  mufcles , and  having  in  vain  attempted  to 
make  any  opiate  continue  in  her  ftbmaeh,  an  ounce  of  lauda- 
num 


Sect.  III.  5.  MOTIONS  OF  THE  RETINA.  19 

num  was  rubbed  along  the  fpine  of  her  back,  and  a dram  of 
it  was  ufed  as  an  enema;  by  this  medicine  a kind  of  drunken 
delirium  was  continued  many  hours , and  when  it  ceafed  the 
convulfions  did  not  return  ; and  the  lady  continued  well  many 
years,  except  fome  {lighter  relapfes,  which  were  relieved  in 
the  fame  manner. 

Mifs  H ,-tan  accomplifhed  young  lady,  with  light  eyes 

and  hair,  was  feized  with  convulfions  of  her  limbs,  with  hic- 
cough, and  efforts  to  vomit,  more  violent  than  wmrds  can  ex- 
prefs  ; thefe  continued  near  an  hour,  and  were  fucceeded  with 
a cataleptic  fpafm  of  one  arm,  with  the  hand  applied  to  her 
head ; and  after  about  twenty  minutes  thefe  Ipafms  ceafed, 
and  a talkative  reverie  fupervened  for  near  another  hour, 
from  which  no  violence,  which  it  w*as  proper  to  ufe,  could 
awaken  her.  Thefe  periods  of  convulfions,  hrft  of  the  muf- 
cles,  and  then  of  the  ideas,  returned  twice  a day  for  feveral 
weeks ; and  were  at  length  removed  by  great  dofes  of  opium, 
after  a great  variety  of  other  medicines  and  applications  had 
been  in  vain  experienced.  This  lady  was  fubjetd  to  frequent 
relapfes,  once  or  twice  a year,  for  many  years,  and  was  as 
frequently  relieved  by  the  lame  method. 

Mifs  W , an  elegant  young  lady,  with  black  eyes  and 

hair,  had  fometimes  a violent  pain  of  her  fide,  at  other  times  a 
moft  painful  ftrangury,  which  were  every  day  fucceeded  by  de- 
lirium; which  gave  a temporary  relief  to  the  painful  fpafrns. 
After  the  vain  exhibition  of  variety  of  medicines  and  applica- 
tions by  different  phyhcians,  for  more  than  a twelvemonth, 
fire  was  directed  to  take  fome  dofes  of  opium,  which  were 
gradually  increafed,  by  which  a drunken  delirium  was  kepc 
tip  for  a day  or  two,  and  the  pains  prevented  from  returning. 
A flcfh  diet,  with  a little  wine  or  beer,  inftead  of  the  low 
regimen  fhe  had  previqufly  ufed,  in  a few  weeks  completely 
eftablifhed  her  health  ; which,  except  a few  relapfes,  has 
continued  for  many  years. 

9.  Lalfly,  as.  we  advance  in  life  all  the  parts  of  the  body 
become  more  rigid,  and  are  rendered  Ms  fufceptible  of  new 
habits  of  motion,  though  they  retain  thofe  that  were  before 
eftabli/hed.  This  is  fenfibly  obferved  by  thofe  who  apply 
thenffelves  late  in  life  to  mufic,  fencing,  or  any  of  the  me- 
chanic arts.  In  the  fame  manner  may  elderly  people  retain 
the  ideas  they  had  learned  early  in  life,  but  find  great  diffi- 
culty in  acquiring  new  trains  of  memory ; infomuch  that  in 
extreme  old  age  we  frequently  fee  a forgetfulnefs  of  the  buh- 
nefs  of  vefterday,  and  at  the  fame  time  a circumftantial  re- 
membrance of  the  amufements  of  their  youth ; till  at  length 

E the 


20 


MOTIONS  OF  THE  RETINA.  Sect.  III.  6 

the  ideas  of  recolleiSIion  and  adlivity  of  the  body  gradually 
ceafe  together, — fuch  is  the  condition  of  humanity  ! — and 
nothing  remains  hut  the  vital  motions  and  fenfations. 

VI.  r.  In  oppofition  to  this  dodfrine  of  the  production  o: 
our  ideas,  it  may  be  afked,  if  fome  of  our  ideas,  like  other 
animal  motions,  are  voluntary,  why  can  we  not  invent  new 
ones,  that  have  not  been  received  by  perception  ? The  an- 
Iwer  will  be  better  underftood  after  having  perufed  the  iuc- 
ceeding  fedtion,  where  it  will  be  explained,  that  the  mufculur 
motions  likewife  are  originally  excited  by  the  ftimulus  of  bo- 
dies external  to  the  moving  organ;  and  that  the  will  has  only 
the  power  of  repeating  the  motions  thus  excited. 

2.  Another  objector  may  afk,  Can  the  motion  of  an  organ 
of  fenfe  rel'emble  an  odour  or  a colour  ? To  which  I can  onlv 
anfvver,  that  it  has  not  been  demonftrated  that  any  of  our 
ideas  refemble  the  objedts  that  excite  them ; it  has  generally 
been  believed  that  they  do  not;  but  this  fhall  be  difcufled  at 
large  in  Sect.  XIV. 

3.  There  is  another  objedtion  that  at  flrit  view  would  feeir. 
lefs  eafy  to  furmount.  After  the  amputation  of  a foot  or  a 
finger,  it  has  frequently  happened,  that  an  injury  being  offered 
to  the  flump  of  the  amputated  limb,  whether  from  cold  air,  too 
great  preffure,  or  other  accidents,  the  patient  has  complained  of 
a fenfation  of  pain  in  the  foot  or  finger  that  was  cut  off.  Dees 
not  this  evince  that  all  our  ideas  are  excited  in  the  brain,  and 
not  in  the  organs  of  fenfe  ? This  objection  is  anfwered  by 
obferving,  that  our  ideas  of  the  fhape,  place,  and  folidity  of 
our  limbs,  are  acquired  by  our  organs  of  touch  and  of  light, 
which  are  fituated  in  our  lingers  and  eyes,  and  not  by  any 
ienfations  in  the  limb  itl'elf. 

In  this  cafe  the  pain  or  fenfation  which  formerly  has  arifeit 
in  the  foot  or  toes,  and  been  propagated  along  the  nerves  to 
the  central  part  of  the  fenforium,  was  at  the  fame  time  accom- 
panied with  a viiible  idea  of  the  fhape  and  place,  and  with  a 
tangible  idea  of  the  folidity  of  the  affedled  limb : now,  when 
thele  nerves  are  afterwards  affedfed  by  any  injury  done  to  die 
remaining  flump  with  a fimilar  degree  or  kind  of  pain,  the  ideas 
of  the  fhape,  place,  or  folidity  of  the  loll  limb,  return  by  af~ 
fociation ; as  thefe  ideas  belong  to  the  organs  of  light  anc 
touch,  on  which  they  were  firfl  excited. 

4.  If  you  wonder  what  organs  of  fenfe  can  be  excited  into 
motion,  when  vou  call  up  the  ideas  of  wifdom  or  beneve 
lence,  which  Mr.  Locke  has  termed  abflracfed  ideas  ; I afk 
you  by  what  organs  of  fenfe  you  firft  became  acquainted 
with  thefe  ideas ? And  the  anfwer  will  be  reciprocal;  tor  it  is 

certain 


Sect.  IV. 


ANIMAL  CAUSATION. 


21 


certain  that  all  our  ideas  were  originally  acquired  by  our  or- 
gans of  fenfe ; for  whatever  excites  our  perception  mu  ft  be 
external  to  the  organ  that  perceives  it,  and  we  have  no  other 
inlets  to  knowledge  but  by  our  perceptions : as  will  be  fur- 
ther explained  in  Section  XIV.  and  XV.  on  the  Productions 
and  Gaffes  of  Ideas. 

VII.  If  our  recollection  or  imagination  be  not  a repetition 
of  animal  movements,  I afk,  in  my  turn,  What  is  it?  You 
tell  me  it  coniifts  of  images  or  pictures  of  things.  Where  is 
this  extenfive  canvafs  hung  up  ? or  where  are  the  numerous 
receptacles  in  which  thofe  are  depofked  ? or  to  what  elfe  in 
the  animal  fyftem  have  they  any  fimilitude  ? 

That  pleating  picture  of  objects,  reprefented  in  miniatiue  , 
on  the  retina  of  the  eye,  feems  to  have  given  rife  to  this  illu- 
ffve  oratory ! It  was  forgot  that  this  reprefentation  belongs  ra- 
ther to  the  laws  of  light,  than  to  thofe  of  life  ; and  may  with 
equal  elegance  be  feen  in  the  camera  obfeura  as  in  the  eye , 
and  that  the  picture  vanifhes  for  ever,  when  the  object  is 
withdrawn. 


SECT.  IV, 

LAWS  OF  ANIMAL  CAUSATION. 

I.  The  fibres,  which  conftitttte  the  mufcles  and  organs  of 
fenfe,  poffefs  a power  of  contraction.  The  circumftances 
attending  the  exertion  of  this  power  of  contraction  eon- 
ftitute  the  laws  of  animal  motion  ; as  the  circumftances  at- 
tending the  exertion  of  the  power  of  attraction  confti- 
tute  the  laws  of  motion  of  inanimate  matter. 

II.  The  fpirit  of  animation  is  the  immediate  caufe  of  the 
contraction  of  animal  fibres ; it  reftdes  in  the  brain  and  nerves, 
and  is  liable  to  general  or  partial  diminution  or  accumulation. 

III.  The  ftimulus  of  bodies  external  to  the  moving  organ  is 
fne  remote  caufe  of  the  original  contractions  of  animal  fibres. 

IV.  A certain  quantity  of  ftimulus  produces  irritation, 
which  is  an  exertion  of  the  fpirit  of  animation  exciting  the 
fibres  into  contraction. 

V.  A certain  quantity  of  contraction  of  animal  fibres,  if 
it  be  perceived  at  all,  produces  pleafure ; a greater  or  lefs 
quantity  of  contraction,  if  it  be  perceived  at  all,  produces 
pain  ; thefe  conftitute  fenfation. 

VI.  A certain  quantity  of  fenfation  produces  defire  or  a- 
verfion  ; thefe  conftitute  volition. 

VII  All  animal  motions  which  have  occurred  at  the  fame 
time,  or  in  immediate  fucceflion,  become  fo  connected,  that 

when 


22 


SENSORIAL  FACULTIES. 


Sect.  V. 


when  cne  of  them  is  reproduced,  the  other  has  a tendency  to 
accompany  or  fucceed  it.  When  fibrous  contractions  iuc- 
ceed  or  accompany  other  fibrous  contractions,  the  connec- 
tion is  termed  affociation  ; when  fibrous  contractions  fucceed 
fenforial  motions,  the  connection  is  termed  cauiation ; when 
fibrous  2nd  feniorial  motions  reciprocally  introduce  each  other, 
it  is  termed  catenation  of  animal  motions.  All  thele  connec- 
tions are  faid  to  be  produced  by  habit,  that  is,  by  rrequent  re- 
petition. Thele  laws  of  animal  cauiation  will  be  evinced  by 
numerous  faffs,  which  occur  in  our  daily  exertions ; and  v ill 
afterwards  be  employed  to  explain  the  more  recondite  phe- 
nomena of  the  production,  growth,  difeal'es,  and  decay  of 
the  animal  lyfretn. 


SECT.  V. 

OF  THE  FOUR  FACULTIES  OR  MOTIONS  OF  THE 
SENSORIUM. 

X.  Four  fenforial  powers.  2.  Irritation,  fenfation,  volition, 

affociation  defined.  3.  Scnforial  motions  dijlinguijhed 
from  fibrous  motions. 

1.  THE  fpirit  of  animation  has  four  different  modes  of  ac- 
tion ; or,  in  other  words,  the#nimal  fenforium  poffeffes  four 
different  faculties,  which  are  occafionally  exerted,  and  caufe 
all  the  contradfions  of  the  fibrous  parts  of  the  body.  Thefe 
are  the  faculty  of  caul'mg  fibrous  contractions  in  confequence 
of  the  irritations  excited  by  external  bodies,  in  confequence  of 
the  fenfations  of  plealure  or  pain,  in  confequence  of  volition,  and 
in  confequence  of  the  affociations  of  fibrous  contractions  with 
other  fibrous  contractions,  which  precede  or  accompany  them. 

Thefe  four  faculties  of  the  fenforium  during  their  inactive 
Hate  are  termed  irritability,  fenfibility,  voluntarily,  and  affo- 
ciability ; in  their  active  Rate  they  are  termed  as  above,  irri- 
tation, fenfation,  volition,  affociation. 

2.  Irritation  is  an  exertion  or  change  of  feme  extreme 
part  of  the  fenforium  refining  m the  mufcles  or  organs  of 
fenfe,  in  confequence  of  the  appulfes  of  external  bodies. 

Sensation  is  an  exertion  or  change  of  the  central  parts 
of  the  fenforium,  or  of  the  whole  of  it,  beginning  at  iome 
of  thofe  extreme  £>arts  of  it,  which  rel.de  in  the  mulcles  or 
organs  of  fenfe. 

Volition  is  an  exertion  or  change  of  the  central  parts  of 
the  fenforium,  or  of  the  whole  of  it,  terminating  in  lome  of 
thofe  extreme  parts  of  it,  which  refide  in  the  muicles  or  organs 
of  fenfe.  Association 


23 


Sect.  VI.  i.  SENSORIAL  FACULTIES. 

Association  is  an  exertion  or  change  of  forae  extreme 
part  of  the  fenforium  refiding  in  the  mufcies  or  organs  of 
fenfe,  in  confequence  of  fome  ; antecedent  or  attendant  fibrous 
contradfions. 

3.  Thefe  four  faculties  of  the  animal  fenforium  may,  at  the 
time  of  their  exertions,  be, termed  motions,  without  impropriety 
of  language  ; for  we  cannot  pafs  from  a ffate  of  inienfibility  or 
inadtion,  to  a Rate  of  feniibility  or  of  exertion,  without  fome 
change  of  the  fenforium,  and  every  change  includes  motion. 
We  (hall  therefore  fometimes  term  the  above  defcribed  facul- 
ties fcnforial  motions,  to  diftinguifh  them  from  fibrous  mo- 
tions ; which  latter  exprefllon  includes  the  motions  of  the 
mufcies  and  organs  of  fenfe. 

The  adtive  motions  of  the  fibres,  whether  thofe  of  the 
mufcies  or  organs  of  fenfe,  are  probably  fimple  contradfions ; 
the  fibres  being,  again  elongated  by  antagoniff  mufcies,  by  cir- 
culating fluids,  or  fometimes  by  elaftic  ligaments,  as  in  the 
necks  of  quadrupeds.  The  fenforial  motions,  which  • confti- 
tute  the  fenfations  of  pleafure  or  pain,  and  which  conftitute 
volition,  and  which  caufe  the  fibrous  contradfions  in  confe- 
quence  of  irritation  or  of  afTociation,  are  not  here  fuppofed 
to  be  fludfuations  or  refludfuations  of  the  fpirit  cf  animation; 
nor  are  they  fuppofed  to  be  vibrations  of  revibrations,  nor 
condenfations  or  equilibrations  of  it;  but  to  be  changes  or 
motions  of  it  peculiar  to  life. 


SECT.  VI. 

OF  THE  FOUR  CLASSES  OF  FIBROUS  MOTIONS. 

I.  Origin  of  fibrous  contrafiions.  II.  Dijtribution  of  them 
into  four  claffes , irritative  motions,  fenfitive  motions , 
voluntary  motions , and  qfifociate  motions , defined. 

I.  ALL  the  fibrous  contradfions  of  animal  bodies  originate 
from  the  fenforium,  and  refolve  themfelves  into  four  claffes,  cor- 
refpondent  with  the  four  powers  or  motions  of  the  fenforium 
above  defcribed,  and  from  which  they  have  their  caufation. 

1.  Thefe  fibrous  contradfions  were  originally  caufed  by  the 
irritations  excited  by  objedfs,  which  are  external  to  the  moving 
organ.  As  the  pulfations  of  the  heart  are  owing  to  the  irritations 
excited  by  the  ifimulus  of  the  blood ; and  the  ideas  of  perception 
are  owing  to  the  irritations  excited  by  external  bodies. 

2.  Eut  as  painful  or  pleafureable  fenfations  frequently  ac- 
companied thofe  irritations,  by  habit  thefe  fibrous  contractions 
became  caufcable  by  the  fenfations,  and  the  irritations  ceafed 

» to 


24  FIBROUS  CONTRACTIONS.  Sect.  VI.  2. 


to  be  neceffary  to  their  production.  As  the  fecretion  of  tears 
iil  grief  is  caufed  by  the  fenfation  of  pain;  and  the  ideas  of  ima- 
gination, as  in  dreams  or  delirium,  are  excited  by  the  pleal'ure 
or  pain  with  which  they  were  formerly  accompanied. 

3.  But  as  the  efforts  of  the  will  frequently  accompanied  thefe 
painful  or  pleafureable  fenfations,  by  habit  the  fibrous  contrac- 
tions became  caufeable  by  volition ; and  both  the  irritations  and 
fenfations  ceafed  to  be  neceffary  to  their  production.  As  the 
deliberate  locomotions  of  the  body,  and  the  ideas  of  recollection, 
as  when  we  wall  to  repeat  the  alphabet  backwards. 

4.  But  as  many  of  thefe  fibrous  contractions  frequently  ac- 
companied other  fibrous  contractions,  by  habit  they  became 
caufeable  by  their  affociarions  with  them;  and  the  irritations, 
fenfations,  and  volition,  ceafed  to  be  neceffary  to  their  produc- 
tion. As  the  aCtions  of  the  mufcles  of  the  lower  limbs  in  fenc- 
ing are  affociated  with  thofe  of  the  arms ; and  the  ideas  of  fug- 
geftion  are  affociated  with  other  ideas,  which  precede  or  ac- 

ng  carelefily  the  alphabet  in  its  ufual 


II.  We  fhall  give  the  following  names  to  thefe  four  claffes 
of  fibrous  motions,  and  fubjoin  their  definitions. 

1.  Irritative  motions.  That  exertion  or  change  of  the  fen- 
forium,  which  is  caufed  by  the  appulfes  of  external  bodies,  either 
limply  fubfides,  or  is  fucceeded  by  fenfation,  or  it  produces 
fibrous  motions;  it  is  termed  irritation,  and  irritative  motions 
are  thofe  contractions  of  the  mufcular  fibres,  or  of  the  organs 
of  fenfe,  that  are  immediately  confeqycnt  to  this  exertion  or 
change  of  the  fenforium. 

2.  Seniitive  motions.  That  exertion  or  change  of  the  fen- 
forium, which  conflitutes  pleafure  or  pain,  either  limply  fub- 
fides, or  is  fucceeded  bv  volition,  or  it  produces  fibroHS  motions ; 
it  is  termed  fenfation,  and  the  fenfitive  motions  are  thofe  con- 
tractions of  the  mufcular  fibres,  or  of  the  organs  of  fenfe,  that 
are  immediately  eonfequent  to  this  exertion  or  change  cf  the 
fenforium. 

3.  Voluntary  motions.  That  exertion  or  change  of  the 
fenforium,  which  conftitutes  defire  or  averfion,  either  fimplv 
fubfides,  or  is  fucceeded  by  fibrous  motions ; it  is  then  termed 
volition,  and  voluntary  motions  are  thofe  contractions  of  the 
mufcular  fibres,  or  of  the  organs  of  fenfe,  that  are  immediately 
eonfequent  to  this  exertion  or  change  of  the  fenforium. 

4.  Affociate  motions.  That  exertion  or  change  of  the  len- 
forium,  which  accompanies  fibrous  motions,  either  fimplv  fub- 
fides, or  is  fucceeded  by  fenfation  or  volition,  or  it  produce^ 
other  fibrous  motions ; it  is  then  termed  affociation,  and  the 


affociate 


Sect.  VII.  i.  IRRITATIVE  MOTIONS.  25 

affociate  motions  are  thofe  contractions  of  the  mufculav  fibres, 
or  of  the  organs  of  ienfe,  that  are  immediately  consequent  to 
this  exertion  or  change  of  the  fenforium. 


SECT.  VII. 

OF  IRRITATIVE  MOTIONS. 

I.  I.  Son ie  mufcular  motions  are  excited  by  perpetual  irrita- 
tions. 2.  Others  more  frequently  by  fenfations.  3.  Others 
by  volition.  Cafe  of  involuntary  f retches  in  -paralytic 
limbs.  4.  Some  fenfual  motions  are  excited  by  perpetual 
irritations.  5.  Others  more  frequently  by  fenjation  or 
volition. 

II.  I.  Mufcular  motions , excited  by  perpetual  irritations , 
occafonally  become  obedient  to  fenjation  and  to  volition. 
2.  And  the  fenfual  motions. 

III.  I.  Other  mufcular  motions  are  affociated  with  the  irri- 
tative ones.  2.  And  other  ideas  with  irritative  ones. 
Of  letters,  language , hieroglyphics.  Irritative  ideas  exijl 
■without  our  attention  to  them. 

1.  1.  MANY  of  our  mufcular  motions  are  excited  by  per- 
petual irritations,  as  thofe  of  the  heart  and  arterial  fyftem  by  the 
circumfluent  blood.  Many  other  of  them  are  excited  by  inter- 
mittent irritations,  as  thofe  of  the  Stomach  and  bowels  by  the 
aliment  we  fwallow;  of  the  bile-du6ts  by  the  bile;  ot  the  kid- 
neys, pancreas,  and  manv  other  glands,  by  the  peculiar  fluids 
they  Separate  from  the  blood ; and  thofe  of  the  lacteal  and 
othei"  abforbent  veflels  by  the  chyle,  lymph,  and  moifture  of 
tire  atmofphere.  Thefe  motions  are  accelerated  or  retarded, 
as  their  correspondent  irritations  are  increafed  or  diminished, 
without  our  attention  or  confcioufnefs,  in  the  fame  manner  as 
the  various  Secretions  of  fruit,  gum,  refin,  wax,  and  honey, 
are  produced  in  the  vegetable  world,  and  as  the  juices  of  the 
earth  and  the  moifture  of  the  atmofphere  are  abforbed  by  their 
roots  and  foliage. 

2.  Other  mufcular  motions,  that  are  moft  frequently  con- 
nected with  our  fenfations,  as  thofe  of  the  fphindters  of  the 
bladder  and  anus,  and  the  mufeuli  eredtores  penis,  were  ori- 
ginally excited  into  motion  by  irritation,  for  young  children 
make  water,  and  have  other  evacuations  without  attention  to 
thefe  circumffances  ; “ et  primis  etiam  ab  incunabulis  tendun- 
ter  frepius  puerorum  penes,  amore  nondum  expergefaCto.” 
So  the  nipples  of  young  women  are  liable  to  become  turgid  by 

irritation, 


26 


IRRITATIVE  MOTIONS.  Sect.  VII.  i, 

irritation,  long  before  they  are  in  a fituation  to  be  excited  by 
the  pleafure  of  giving  milk  to  the  lips  of  a child. 

3.  The  contractions  of  the  laiger  muicles  of  our  bodies, 
that  are  mod  frequently  connefted  with  volition,  were  origi- 
nally excited  into  aCtion  by  internal  irritations  ; as  appears 
from  the  ftretching  cryawning  of  all  animals  after  long  C cep. 
In  the  beginning  of  fome  fevers  this  irritation  of  the  mufcles 
produces  perpetual  ftretching  and  yawning ; in  other  periods 
of  fever  an  univerfal  reftleffnefs  arifes  from  the  fame  caufe, 
the  patient  changing  the  attitude  of  his  body  every  minute. 
The  repeated  ftruggles  of  the  fcetus  in  the  uterus  rnuft  be  ow- 
ing to  this  internal  irritation  : for  the  foetus  can  have  no  other 
inducement  to  move  its  limbs  but  the  toedium  or  irkfomenefs 
of  a continued  pofture. 

The  following  cafe  evinces,  that  the  motions  of  ftretching 
the  limbs  after  a continued  attitude  are  not  always  owing  to 
the  power  of  the  will.  Mr  Dean,  a mafon,  of  Auftry  in 
Leicefterfhire,  had  the  fpine  of  the  third  vertebra  of  dre  back 
inlarged ; in  fome  weeks  his  lower  extremities  became  feeble, 
and  at  length  quite  paralytic  : neither  die  pain  of  blifters,  the 
heat  of  fomentations,  nor  the  utmoft  efforts  of  the  will  could 
produce  the  leaft  motion  in  thefe  limbs  ; yet  twice  or  thrice  a 
day,  for  many  months,  his  feet,  legs,  and  thighs  were  affedl- 
ed,  for  many  minutes,  with  forcible  ftretchings,  attended  with 
the  fenfation  of  fatigue  ; and  he  at  length  recovered  the  ul'e 
of  his  limbs,  though  the  fpine  continued  protuberant.  The 
fame  circumftance  is  frequently  feen  in  a lefs  degree  in  the 
common  hemiplagia  ; and  when  this  happens,  I have  believed 
repeated  and  ftrong  fliocks  of  electricity  to  have  been  of 
great  advantage. 

4.  In  like  manner  the  various  organs  of  fenfe  are  originally 
excited  into  motion  by  various  external  ftimuli  adapted  to  this 
purpofe,  which  motions  are  termed  perceptions  or  ideas ; and 
.many  of  thefe  motions,  during  our  waking  hours,  are  excited  by 
perpetual  irritation,  as  thofe  of  the  organs  cl  hearing  and  of 
touch.  The  former  by  the  conftant  low  indiftind  noifes  that 
murmur  around  us,  and  the  latter  by  the  weight  of  our  bodies 
on  the  parts  which  iupport  them  ; and  by  the  unceaftng  varia- 
tion? of  the  heat,  moitiure,  and  preffure  of  the  atmoiphere ; and 
thefe  fenfual  motions,  pteciiely  as  the  mufeuiar  ones  above  men- 
tioned, obey  their  correfpondent  irritations  without  our  atten- 
tion or  conlcioufneis. 

5.  Other  claffes  of  our  ideas  are  more  frequently  excited  by 
our  fenfations  of  pleafure  or  pain,  and  others  by  volition:  but 
that  theie  have  all  been  originally  excited  by  ftimuli  from  ex- 
ternal 


Sect.  VII.  2.3.  IRRITATIVE  MOTIONS.  27 

ternal  objedls,  and  only  vary  in  their  combinations  cr  repara- 
tions, has  been  fuilv  evinced  by  Mr.  Locke;  and  are  by  him 
termed  the  ideas  of  perception,  in  contradiftindfioa  to  thofe 
which  he  calls  the  ideas  of  reflection. 

II.  1.  Thefe  mufcular  motions,  that  are  excited  by  perpe- 
tual irritation,  are  neverthelefs  occalionally  excitable  by  the 
fenfations  of  pleafnre  or  pain,  or  by  volition,  as  appears  by 
the  palpitation  of  the  heart  from  fear,  the  increaled  lecredon 
of  ialiva  at  the  light  of  agreeable  food,  and  the  glow  on  the 
fkin  of  thofe  who  are  afhamed.  There  is  an  inftance  told 
in  the  Philofophical  Tranfadfions,  of  a man,  who  could  for  a. 
time  flop  the  motion  of  the  heart  when  he  plealed ; and  Mr. 
D.  has  often  told  me,  he  could  io  far  increafe  the  periftaltic: 
motion  of  his  bowels  by  voluntary  efforts,  as  to  produce  an 
evacuation  by  ftool  at  any  time  in  half  an  hour. 

2.  In  like  manner  the  fenfuai  motions,  or  ideas,  that  are 
excited  by  perpetual  irritation,  are  nevertheless  occalionally 
excitable  by  fenfation  or  volition  ; as  in  the  night,-  when  we 
liften  under  the  influence  of  fear,  or  from  voluntary  attention, 
the  motions  excited  in  the  organ  of  hearing  by  the  whifper- 
ing  of  the  air  in  our  room,  the  pulfation  of  our  own  arteries, 
of  the  faint  beating  of  a diftant  watch,  become  objedts  o£ 
perception. 

III.  1.  Innumerable  trains  or  tribes  of  ether  motions  are 
a (foci  a ted  with  thefe  mufcular  motions,  which  are  excited  by 
irritation  ;■  as  by  the  ftimulus  of  the  blood  in  the  right  cham-  1 
her  of  the  heart,  the  lungs  are  induced  to  expand  themfelyes ; 
and  the  pedforal  and  intercoftal  mulcles,  and  the  diaphragm, 
adl  at  the  fame  time  by  their  aflociations  with  them.  And 
when  the  pharinx  is  irritated  by  agreeable  food,  the  mufcles 
of  deglutition  are  brought  into  adfion  by  affcciation.  Thus 
when  a greater  light  fails  on  the  eye,  the  iris  is  brought  into 
adfion  without  our  attention ; and  the  ciliary  procefs,  when 
the  focus  is  formed  before  or  behind  the  retina,  by  their  aflfo- 
ciations  with  the  increased  irritative  motions  of  the  organ  of 

' ifion.  Many  common  actions  of  life  are  produced  in  a funilar 
manner.  If  a fly  fettle  on  my  forehead,  w hi  1ft  I am  intent  on 
tr.y  prelent  occupation,  I difledge  it  with  my  finger  without  ex- 
citing my  attention  or  breaking  the  train  of  my  ideas. 

2.  In  like  manner  the  irritative  ideas  luggeft  to  us  many 
other  trains  or  tribes  of  ideas  that  are  aflfociated  with  them. 
On  this  kind  of  eonnedfion,  language,  letters,  hieroglyphics, 
and  every  kind  of  fymbol,  depend.  The  fymbols  themlelves 
produce  irritative  ideas,  or  fenfuai  motions,  which  v\e  do  not 
attend  to ; and  other  ideas,  that  are  iucceeded  by  fenlation, 

F are 


28 


SENSITIVE  MOTIONS.  Sect.  VIII.  r, 


are  excited  by  their  affociation  with  them.  And  as  thefe  irri- 
tative ideas  make  up  a part  of  the  chain  of  our  waking 
thoughts,  introducing  other  ideas  that  engage  our  attention, 
though  themfelves  are  unattended  to,  we  find  it  very  difficult 
to  inveftigate  by  what  fteps  many  of  our  hourly  trains  c: 
;deas  gain  their  admittance. 

It  may  appear  paradoxical,  that  ideas  can  exift,  and  not  be 
attended  to  • but  all  our  perceptions  are  ideas  excited  by  irri- 
tation, and  lucceeded  by  fenfation.  Now,  when  thefe  ideas, 
excited  by  irritation,  give  us  neither  pleafure  nor  pain,  we  ceale 
to  attend  to  them.  Thus  whilft:  I am  walking  through  that 
grove  before  my  window,  I do  not  run  againft  the  trees  or  the 
benches,  though  my  thoughts  are  ftrenuoufly  exerted  on  fome 
other  objedl.  This  leads  us  to  a dillindf  knowledge  of  irrita- 
tive ideas  ; for  the  idea  of  the  tree  or  bench,  which  I avoid, 
exifts  on  my  retina,  and  induces,  by  affociation,  the  action  of 
certain  locomotive  mufcles  ; though  neidrer  itfelf,  nor  the 
actions  of  thofe  mufcles,  engage  my  attention. 

Thus,  whilft  we  are  converting  on  this  fulfiedt,  the  tone, 
note,  and- articulation  of  every  individual  word  forms  its  cor- 
refpondent  irritative  idea  on  the  organ  of  hearing  ; but  we  on- 
ly attend  to  the  affociatcd  ideas,  that  are  attached  bv  habit  to 
thefe  irritative  ones,  and  are  fucceedcd  by  fenfation  : thus 
when  we  read  the  words  “ printing-press/’  we  do  not 
attend  to  the  fhape,  fize,  or  exiftence  of  the  letters  which 
compofe  thefe  words,  thougir  each  of  them  excites  a correl'- 
pondent  irritative  motion  of  our  organ  of  vilion  ; but  they 
introduce  by  affociation  our  idea  of  the  mod;  ufeful  of  modern 
inventions ; the  capacious  refervoir  ot  human  knowledge, 
whole  branching  dreams  diffufe  fciences,  arts,  and  moruiitv, 
through  all  nations  and  all  ages. 


SECT.  VIII. 

OF  SENSITIVE  MOTIONS. 

I.  i.  Senftive  mufcular  motions  were  originally  excited  into 
aiiion  by  irritation.  1.  And  fenjitive  fenjual  motions, 
' ideas  cf  imagination,  dreams.  II.  I.  Senjitive  mufcular 
motions  are  occcf anally  obedient  to  volition.  2.  And 
fenjitive  fenfual  motions.  III.  I.  Other  mufcular  mo- 
tions are  aff'oeiated  with  the  fenjitive  ones . 2.  And  ether 
Jenfual  motions. 

I.  i.  MANY  of  the  motions  of  our  mufcles,  that  are  ex- 
cited. into  action  by  irritation,  are  at  tire  lame  time  accompa- 
nied 


29 


Sect.  VIII.  2.  SENSITIVE  MOTIONS. 

nied  with  painful  or  pleafurable  fenfations  ; and  at  length  be- 
come by  habit  caufable  by  the  fenfations.  Thus  the  motions 
of  the  fphindters  of  the  bladder  and  anus  were  originally  ex- 
cited into  action  by  irritation  : for.  young  children  give  no  at- 
tention to  thefe  evacuations  but  as  foon  as  they  become  len- 
fible  of  the  inconvenience  of  obeying  theie  irritations,  they 
fuffer  the  water  or  excrement  to  accumulate,  till  it  ditagreea- 
biy  affedts  them ; and  the  action  of  thofe  fpindlers  is  then  in 
confequence  of  this  dilagreeable  fenlation.  So  the  fecretion 
of  the  ialiva,  which  in  young  children  is  copioufly  produced 
by  irritation,  and  drops  from  their  mouths,  is  frequently  at- 
tended with  the  agreeable  fenfation  produced  by  the  maftication 
of  tafteful  food  ; till  at  length  the  fight  of  fuch  food  to  a hun- 
gry perfon  excites  into  ad'tion  thefe  falival  glands  ; as  is  feen 
in  the  Havering  of  hungry  dogs. 

The  motions  of  thole  muicles,  which  afe  affedled  by  laf- 
civious  ideas,  and  thofe  which  are  exerted  in  finding,  weep- 
ing, darting  from  fear,  and  winking  at  the  approach  of  dan- 
ger to  the  eye,  and  at  times  the  adfions  of  every  large  mufcle 
of  the  body,  become  caufable  by  our  fenfations.  And  all 
thefe  motions  are  performed  with  flrength  and  velocity  in  pro- 
portion to  the  energy  of  the  fenfation  that  excites  them,  and 
the  quantity  of  fenforial  power. 

2.  Many  of  the  motions  of  our  organs  of  fenfe,  or  ideas, 
that  were  originally  excited  into  aftion  by  irritation,  become 
in  like  manner  more  frequently  caufable  by  our  fenfations  of 
pleafure  or  pain.  Thefe  motions  are  then  termed  the  ideas  cf 
imagination,  and  make  up  all  the  fcenery  and  tranfactions  of 
our  dreams.  Thus,  when  any  painful  or  pleafurable  fenfations 
pofTefs  us,  as  of  love,  anger,  fear;  whether  in  our  fleep  or 
waking  hours,  the  ideas,  that  have  been  formerly  excited  by 
the  objedfs  of  thefe  fenfations,  now  vividly  recur  before  us-  by 
their  connection  with  the  fefenfations  themfelves.  So  the  fair 
fmiling  virgin,  that  excited  your  love  by  her  prefence,  whenever 
that  fenfation  recurs,  rifes  before  you  in  imagination  ; and  that 
with  all  the  pleafing  circumftances  that  had  beiore  engaged 
your  attention.  And  in  fleep,  when  you  dream  under  the  influ- 
ence of  fear,  all  the  robbers,  fires,  and  precipices,  that  you  for- 
merly have  feen  or  heard  of,  arife  before  vou  with  terrible  viva- 
city. All  thefe  fenfual  motions,  like  the  mufcular  ones  above 
mentioned,  are  performed  with  Strength  and  velocity  in  propor- 
tion to  the  energy  of  the  fenfation  of  pleafure  or  pain  which 
excites  them,  and  the  quantity  of  fenforial  power. 

II.  1.  Many  of  thefe  mufcular  motions  above  deferibed,  that 
are  moft  frequently  excited  by  our  fenfations,  are  nevertheless 

occaiionally 


VOLUNTARY  MOTIONS.  Sect.  IX. 


3° 

occafionally  caufable  by  volition;  for  we  can  fmile  or  frown 
fpontaneoufly,  can  make  water  before  the  quantity  or  acrimony 
of  the  urine  produces  a di  ('agreeable  fenfacion,  and  can  volun- 
tarily mafticate  a naufeous  drug,  or  fwallow  a bitter  draught, 
though,  our  fenfation  would  flrongly  diffuade  us. 

2.  In  like  manner  the  lenfual  motions,  or  ideas,  that  are  mod 
frequently  excited  by  our  fenfations,  are  neverthelefs  occaf. on- 
ally  caufable  by  volition,  as  we  can  fponraneoullv  call  up  our 
lull  night's  cream  before  us,  tracing  it  induftriouflv,  ftcp  bv  Itep, 
through  ail  its  variety  of  fcenery  and  tranfaction  ; or  can  volun- 
tarily examine  or  repeat  the  ideas  that  have  "been  excited  by 
our  difguft  or  admiration. 

III.  i.  Innumerable  trains  or  tribes  of  motions  are  aff  icicvd 
with  thefe  fendtive  mufcular  motions  above  mentioned  ; as  when 
a drop  of  water  falling  into  the  wind-pipe  difagreeably  affefts 
the  air-veffels  of  the  lungs,  they  are  excited  into  violent  action 
and  with  thefe  fenfitive  motions  are  a Hoc  i a ted  die  actions  of  the 
pectoral  and  intercoftal  mufcles,  and  the  diaphragm ; tiil  by  their 
united  and  repeated  fuccuffions,  the  drop  is  returned  through 
the  larinx.  The  fame  occurs  when  any  thing  diiagreeablv 
affcifts  the  noitriis  or  the  ftomach,  cr  the  uterus : variety  of 
mufcles  are  excited  by  affociation  into  forcible  action,  not  to  be 
fuppreffed  by  the  utmoft  efforts  of  the  will;  as  in  fneezing, 
vomitipg,  and  parturition. 

2.  In  like  manner  with  thefe  fenfitive  fenfual  motions,  cr 
ideas  of  imagination,  are  affociated  many  ether  trams  or  t rib  ex 
cf  ideas,  which  by  fome  writers  ct  metaphyfics  have  been  chile  i 
under  the  terms  of  relemblance,  caufation,  and  contiguity ; and 
will  be  more  iully  treated  of  hereafter. 


SECT.  IX. 

OF  VOLUNTARY  MOTIONS. 

I.  I.  Voluntary  mufcular  motions  are  originally  excited  hy 
irritations.  2.  And  voluntary' ideas.  Gf  reafon.  II.  i. 
Voluntary  mufcular  motions  are  occajionally  caufable  by 
fenfatlons.  2.  And  voluntary  ideas.  1IJ,  I.  Voluntary 
mufcular  motions’  are  occafionally  obedient  to  irritations. 
2.  And  voluntary  ideas.  IV.  I.  Voluntary  mufcular  mo- 
tions are  affociated  with  other  mufcular  motions.  2.  And 
voluntary  ideas. 

WHEN  pleafure  or  pain  affect  the  animal  fvftem,  many 
of  its  motions,  both  mufcular  and  fenfual,  are  brought  into  ac  - 
don;  as  was  ihewn  in  the  preceding  lection,  and  were  caikd 
' ' ' • ' ' fenfitive 


Sect.  IX.  i.  VOLUNTARY  MOTIONS.  31 

fenfitive  motions.  The  general  tendency  of  thefe  motions  is 
to  arreft  and  to  poffefs  the  pleafure,  or  to  diflodge  or  avoid  the 
pain  : but  if  this  cannot  immediately  be  accompli  hied,  defire 
or  averfion  are  produced,  and  the  motions  in  confequence  of 
this  new  faculty  of  the  fenforium  are  called  voluntary. 

1.  1.  TholVmufcles  of  the  body  that  are  attached  to  bones, 
have  in  general  their  principal  connection  with  volition;  as,  I 
move  my  pen  or  raife  my  body.  Thefe  motions  were  origi- 
nally excited  by  irritation,  as  was  explained  in  the  lection  cn 
that  lubjecV,  -afterwards  the  fenlations  of  pleafure  or  pain, 
that  accompanied  the  motions  thus  excited,  induced  a repeti- 
tion of  them;  and  at  length  many  of  them  were  voluntarily 
pradtifed,  in  iucceffion  or  in  combination,  for  the  common  pur- 
pofes  of  life,  as  in  learning  to  walk,  or  to  fpeak ; and  are 
performed  with  ftrength  and  velocity  in  proportion  to  the 
pnergy  of  the  volition  that  excites  them,  and  the  quantity  of 
feniorial  power. 

2.  Another  great  clafs  of  voluntary  motions  confifls  of  the 
ideas  of  recolledtionl  We  will  to  repeat  a certain  train  of 
ideas,  as  of  the  alphabet  backwards  ; and  if  any  ideas,  that 
do  not  belong  to  this  intended  train,  intrude  themfelves  by 
other  connections,  we  will  to  rejedf  them,  and  voluntarily 
perfifl  in  the  determined  train.  So  at  my  approach  to  ahoufe 
which  I have  but  once  vifited,  and  that  at  the  diftance  of  ma- 
ny months,  I will  to  recollect  the  names  of  the  numerous  fa- 
mily I expedl  to  fee  there,  and  I do  recollect  them. 

On  this  voluntary  recollection  of  ideas  our  faculty  of  rea- 
fon  depends,  as  it  enables  us  to  acquire  an  idea  of  the  diffi- 
rnilicude  of  any  two  ideas.  Thus  if  you  voluntarily  produce 
the  idea  of  a right-angled-triangle,  and  then  of  a fquare ; and 
after  having  excited  thefe  ideas  repeatedly,  you  excite  the  idea 
of  their  difference,  which  is  that  of  another  right-angled-tri- 
angle inverted  over  the  former ; you  are  f aid  to  reafon  upon 
this  fubjeft,  or  to  compare  your  ideas. 

Thele  ideas  of  recollection,  like  the  mufcular  motions  a- 
bove  mentioned,  were  originally  excited  by  the  irritation  of 
external  bodies,  aqd  were  termed  ideas  of  perception : after- 
wards the  p.eafu  re  or  pain,  that  accompanied  thefe  motions, 
induced  a repetition  of  them  in  the  abfence  of  the  external  bo- 
dy, by  which  they  were  firft  excited : and  then  they  were 
termed  ideas  of  imagination.  At  length  they  became  volun- 
tarily practiied,  in  iucccffioji  or  in  combination,  for  the  com- 
mon purpofes  of  life;  as  when  we  make  ourfelves  matters  of 
the  hiftory  of  mankind,  cr  of  the  fciences  they  have  invefti- 
gated ; and  are  then  called  ideas  of  recollection  ; and  are  per- 
formed 


S2  VOLUNTARY  MOTIONS.  Sect.  IX. 

formed  with  ftrength  and  velocity  in  proportion  to  the  energy 
of  the  volition  that  excites  them,  and  the  quantity  of  fenforial 
power. 

II.  i.  The  mufcular  motions  above  defcribed,  that  are 
moft  frequently  obedient  to  the  will,  are  neverthelefs  occa- 
fionally  caufable  by  painful  or  pleafurable  fenfation,  as  in 
the  flatting  from  fear,  and  the  contradtion  of  die  calf  of  the 
leg  in  the  cramp. 

2.  In  like  manner  the  fenfual  motions,  or  ideas,  that  are 
moft  frequently  connected  with  volition,  are  neverthelefs  oc- 
Caftonaliy  caufable  by  painful  or  pleafurable  fenfation.  As 
the  hiftories  of  men,  or  the  defcription  of  places,  which  we 
have  voluntarily  taken  pains  to  remember,  fometimes  occur 
fo  us  in  our  dreams. 

III.  i.  The  mufcular  motions  that  are  generally  fubfervi- 
erit  to  volition,  are  alfo  occafionally  caulabie  by  irritation,  as 
in  ftretching  the  limbs  after  deep,  and  yawning.  In  this  man- 
ner a contradtion  ot  the  arm  is  produced  by  palling  the  elec- 
tric fluid  from  the  Leyden  phial  along  its  mufcles ; and  that 
even  though  the  limb  is  paralytic.  The  fudden  motion  of  the 
arm  produces  a difagreeable  fenfation  in  the  joint,  but  the 
mufcles  feem  to  be  brought  into  adtion  Amply  by  irritation. 

2.  The  ideas,  that  are  generally  fubfervient  to  the  will,  are 
in  like  manner  occafionally  excited  by  irritation;  as  when  we 
view  again  an  objedt,  we  have  before  well  ftudied,  and  often  re- 
collected. 

IV.  i.  Innumerable  trains  or  tribes  of  motions  are  aflbciated 
with  thefe  voluntary  mufcular  motions  above  mentioned ; as 
when  I will  to  extend  my  arm  to  a diftant  objedt,  lome  other 
mufcles  are  brought  into  action,  and  preferve  the  balance  of 
mv  body.  And  when  I with  to  perform  any  fteadv  exertion, 
as  in  threading  a needle,  or  chopping  with  an  ax,  the  pectoral 
mufcles  are  at  the  fame  time  brought  into  adtion  to  preferve  the 
trunk  of  the  body  motionlefs,  and  we  ceafe  to  reipire  for  a time. 

2.  In  like  manner  the  voluntary  fenfual  motions,  or  ideas, 
of  recolledtion,  are  affociated  with  many  other  mains  or  tribes 
of  ideas.  As  when  I voluntarily  recoiled!  a Gothic  window, 
that  I faw  fome  time  ago,  the  whole  front  of  the  cathedral  occur, 
to  me  at  the  fame  time. 


SECT. 


Sect.  X.  i. 


ASSOCIATE  MOTIONS. 


U 

SECT.  X. 

OF  ASSOCIATE  MOTIONS. 

I.  X.  Many  mufcular  motions,  excited  by  irritations  in  trains 
or  tribes,  become  affiociatecl.  2.  And  many  ideas.  II.  i» 
Many  fenjitive  mufcular  motions  become  officiated.  2. 
And  many  fenjitive  ideas.  III.  I.  Many  voluntary  muf- 
cular motions  become  affiociated.  2.  And  then  become  obe- 
dient to  fenfation  or  irritation.  3.  And  many  voluntary 
ideas  become  ajjociated. 

ALL  the  fibrous  motions,  whether  mufcular  or  fenfual, 
which  are  frequently  brought  into  adtion  together, ' either  in 
combined  tribes,  or  in  fueeeffive  trains,  become  fo  connedted  by 
habit,  that  when  one  of  them  is  re-produced,  the  others  have  a 
tendency  to  fucceed  or  accompany  it. 

1.  1.  Many  of  our  mufcular  motions  were  originally  excited 
in  fucceflive  trains,  as  the  contradlions  of  the  auricles  and  of  the 
ventricles  of  the  heart ; and  others  in  combined  tribes,  as  the 
various  divifions  of  the  mufcles  which  compofe  the  calf  of  the 
kg,  which  were  originally  irritated  into  fynchronous  adtion  by 
the  tedium  or  irkfomenefs  of  a continued  pofture.  By  fre- 
quent repetitions  thefe  motions  acquire  affociations,  which 
continue  during  our  lives,  and  even  after  the  deftruction  of  the 
greateft  part  of  the  fenforium;  for  the  heart  of  a viper  or  frog 
will  continue  to  puifate  long  after  it  is  taken  from  the  body ; 
and  when  it  has  entirely  ceafed  to  move,  if  any  part  of  it  is 
goaded  with  a pin,  the  whole  heart  will  again  renew  its  pulfa- 
tions.  This  kind  of  connedtion  we  ihall  term  irritative 
afTociation,  to  diftinguifh  it  from  fenfitive  and  voluntary,  affo- 
ciations. 

2.  In  like  manner  many  of  our  ideas  are  originally  excited 
in  tribes  ; as  all  the  objedts  of  fight,  after  we  become  fo  well 
acquainted  with  the  laws  of  vilion  as  to  diilinguifh  figure 
and  diftance  as  well  as  colour;  or  in  trains,  as  while  we 
pafs  along,  the  objedts  that  furround  us.  The  tribes  thus 
received  by  irritation  become  affociated  by  habit,  and  have 
been  termed  complex  ideas,  by  the  writers  of  metaphylics,  as 
this  book,  or  that  orange.  The  trains  have  received  no  par- 
ticular name ; but  thefe  are  alike  affociations  of  ideas,  and  fre- 
quently continue  during  our  lives.  So  the  tafte  of  a pine- 
apple, though  we  eat  it  blindfold,  recalls  the  colour  and  fhape 
ot  it;  and  we  can  fcarcely  think  on  folidity  without  a figure. 

II.  1.  By  the  various  efforts  of  our  fenfations  to  acquire 
or  avoid  their  objedts,  many  mufcles  are  daily  brought  into 

lucceffive 


ASSOCIATE  MOTIONS. 


33- 


Sect.  X.  5. 


fucceffivo  or  fynchronous  actions ; thefe  become  affbciated 
by  habit,  and  are  then  excited  together  with  great  facility,  and 
in  many  inftances  gain  indiffoluble  connections.  So  the  play 
of  puppies  and  kittens  is  a reprel'entation  of  their  mode  of 
lighting,  or  of  taking  their  prey ; and  the  motions  of  the  muf- 
cles  neceffary  for  thole  purpofes,  become  alTociated  by  habit, 
and  gain  a great  adroitnefs  of  action  by  thefe  early  repeti- 
tions : fo  the  morions  of  the  abdominal  mufcles,  which  were 
originally  brought  into  concurrent  aftion  with  the  protrufive 
motion  of  the  rectum  or  bladder  by  fenfation,  become  fo  con- 
joined with  them  by  habit,  that  they  not  only  ealily  obey 
thefe  fenfations  occafioned  by  the  hamulus  of  the  excrement 
and  urine,  but  are  brought  into  violent  and  unreftrainable  ac- 
tion in  the  ftranguary  and  tenefmus.  This  kind  of  connec- 
tion we  {hall  term  fenfitive  affociation. 

2.  So  many  of  our  ideas,  that  have  been  excited  together  or 
in  iucceffion  by  our  fenfations,  gain  lynchronous  or  lucceffive 
affociations,  that  are  fometimes  indiffoiuble  but  with  life. 
Hence  the  idea  of  an  inhuman  or  difhonourable  action  perpe- 
tually calls  up  before  us  the  idea  of  the  wretch  that  was  guilty 
of  it.  And  hence  thole  unconquerable  antipathies  are  formed, 
which  fome  people  have  to  the  fight  of  peculiar  kinds  of 
food,  of  which  in  their  infancy  they  have  eaten  to  excels  or 
by  confcraint. 

III.  1.  In  learning  any  mechanic  art,  as  mufic,  dancing, 
or  the  ufe  of  the  fword,  we  teach  many  of  our  mulclcs  to  aft 
together  or  in  lucceflion,  bv  repeated  voluntary  efforts ; which 
by  habit  become  formed  into  tribes  or  trains  ot  affociation, 
and  lerve  ail  our  purpofes  with  great  facility,  and  in  fome  in- 
ftances  acquire  an  indffbluble  union.  Thefe  motions  are 
gradually  formed  into  a habit  of  acting  together  by  a multi- 
tude of  repetitions,  whilft  they  are  yet  feparatelv  caufable  bv 
the  will,  as  is  evident  from  the  long  time  that  is  taken  up 
by  children  in  learning  to  walk  and  to  ipeak;  and  is  experi- 
enced by  every  one  when  he  firffc  attempts  to  fkate  upon  the 
icc  or  to  fwim  ; thefe  we  (hall  term  voluntary  affociations. 

2.  All  thele  mul'cular  movements,  when  they  are  thus  uffo- 
ciated  into  tribes  or  trains,  become  afterwards  not  only  obedi- 
ent to  volition,  but  to  che  fenfations  and  irritations;  and  the 
fame  movement  compofes  a part  ot  manv  different  tribes  cr 
trains  of  motion.  Thus  a litigle  muicle,  when  it  ufe  ai  con- 
fort  with  its  neighbours,  on  one  fide,  affifts  to  move  the  .ur.r 
in  one  direction;  and  in  another,  when  it  acts  with  thofe  ... 
its  neighbourhood  on  die  other  fide  ; and  in  otlier  direct)  om. 
when  it  aits  feparately  or  jointly  with  thole  beat  Le  immcCi- 


ASSOCIATE  MOTIONS. 


Sot.  X.  3. 


35 


ately  under  or  above  it ; and  all  thefe  with  equal  facility  after 
their  affociations  have  been  well  eftablifhed. 

The  facility  with  which  each  mufcle  changes  from  one  af- 
fociated  tribe  to  another,  and  tlvt  either  backwards  or  for- 
wards, is  well  obfervable  in  the  mulcles  of  the  arm  in  moving 
the  windlafs  of  an  air-pump ; and  the  flownefs  of  thofe  mufcu- 
lar  movements,  that  have  not  been  affociated  by  habit,  may  be 
experienced  by  any  one,  who  fhall  attempt  to  faw  the  air 
quick  perpendicularly  with  one  hand,  and  horizontally  with 
the  other  at  the  fame  time, 

3.  In  learning  every  kind  of  fcience,  we  voluntarily  affoci- 
ate  many  tribes  and  trains  of  ideas,  which  afterwards  are  ready 
for  all  the  purpofes,  either  of  volition,  fenfation,  or  irritation; 
and  in  feme  inffances  acquire  indiffoluble  habits  of  adting  to- 
gether, fo  as  to  affedt  out  reafoning  and  influence  our  actions. 
Hence  the  neceffity  of  a good  education. 

Thefe  affociate  ideas  are  gradually  formed  into  habits  of 
adting  together  by  frequent  repetition,  while  they  are  yet  fepa- 
rately  obedient  to  the  will ; as  is  evident  from  the  difficulty  we 
experience  in  gaining  fo  exadt  an  idea  of  the  front  of  St.  Paul’s 
church,  as  to  be  able  to  delineate  it  with  accuracy,  or  in  re- 
colledting  a poem  of  a few  pages. 

And  thefe  ideas,  thus  affociated  into  tribes,  not  only  make 
up  the  parts  of  the  trains  of  volition,  fenfation,  and  irritation  ; 
but  the  fame  idea  compofes  a part  of  many  different  tribes  and 
trains  of  ideas.  So  the  fimple  idea  of  whitenefs  compofes  a 
part  of  the  complex  idea  of  fnow,  milk,  ivory ; and  the  complex 
idea  of  the  letter  A compofes  a part  of  the  feveral  affociated 
trains  of  ideas,  that  make  up  the  variety  of  words,  in  which 
this  letter  enters. 

The  numerous  trains  of  thefe  affociated  ideas  are  divided  by 
Mr.  Hume  into  three  claffes,  which  he  has  termed  contiguity, 
caufation,  and  refemblance.  Nor  fhould  we  wmnder  to  find 
them  thus  connedted  together,  fmee  it  is  the  bufmefs  of  our 
lives  to  difpofe  them  into  thefe  three  claffes ; and  we  become 
valuable  to  ourfelves  and  our  friends,  as  we  fucceed  in  it. 
Thofe  who  have  combined  an  extenfive  clafs  of  ideas  by  the 
contiguity  of  time  or  place,  are  men  learned  in  the  hillcry  of 
mankind,  and  of  the  fciences  they  have  cultivated.  Thefe 
who  have  connedted  a great  clafs  of  ideas  of  refemblances, 
poffefs  the  fource  of  the  ornaments  of  poetry  and  oratory,  and 
of  all  rational  analogy.  While  thofe  who  have  connedted 
great  claffes  of  ideas  of  caufation,  are  furnifhed  with  the 
powers  of  producing  effedts.  Thefe  are  the  men  of  adtive  wif- 

G dom, 


SENSORIAL  ACTIONS. 


Sect.  XI.  i 


36' 

dom,  who  lead  armies  to  vidtory,  and  kingdoms  to  profperitv  , 
or  difcover  and  improve  the  fciences,  which  meliorate  and 
adorn  the  condition  of  humanity. 


SECT.  XL 

ADDITIONAL  OBSERVATIONS  ON  THE  SENSORIAL 
POWERS. 

L Stimulation  is  of  various  kinds,  adapted  to  the  organs  of 
fenfe,  to  the  mufcles,  to  hollow  membranes  and  gland 's. 
Some  objects  irritate  our  fenfes  by  repeated  impulfes.  II. 
I.  Senjation  and  volition  frequently  affedt  the  whole  fen- 
forium.  2.  Emotions,  paffons,  appetites.  3.  Origin  of 
defire  and  dverfion.  Criterion  of  voluntary  aftions,  dif- 
ference of  brutes  and  men.  4.  Senfbility  and  voluntari- 
ly. III.  ykffociations  formed  before  nativity  \ in  itative 
motions  mijlakcn  for  affociated  ones. 

Irritation. 

I.  THE  various  organs  of  fenfe  require  various  kinds  of 
Simulation  to  excite  them  into  adtion;  the  particles  of  light 
penetrate  the  cornea  and  humours  of  the  eye,  and  then  irritate 
the  naked  retina ; fapid  particles,  diffolved  or  diffufed  in  water 
or  faliva,  and  odorous  ones,  mixed  or  combined  with  the  air, 
irritate  the  extremities  of  the  nerves  of  tafte  and  finell ; which 
either  penetrate  or  are  expanded  on  the  membranes  of  the 
tongue  and  noftrils ; the  auditory  nerves  are  {Emulated  by  the 
vibrations  of  the  atmofphere,  communicated  by  means  of  the 
tympanum  and  of  the  fluid,  whether  of  air  or  of  water,  behind 
it;  and  the  nerves  of  touch  by  the  hardnefs  of  furrounding  bo- 
dies, though  the  cuticle  is  interpofed  between  thefe  bodies  and 
the  medulla  of  the  nerve. 

As  the  nerves  of  the  fenfes  have  each  their  appropriated  ob- 
jects, which  {Emulate  them  into  activity ; fo  the  muicular 
fibres,  which  are  the  terminations  of  other  fets  of  nerves,  have 
their  peculiar  objects,  which  excite  them  into  adtion  ; the  lon- 
gitudinal mufcles  are  {Emulated  into  contrsdtion  by  extenfion, 
whence  the  ftretching  or  pendiculation  after  a long  continued 
pofture,  during  \ hich  they  have  been  kept  in  a Rate  of  exten- 
sion ; and  the  hollow  nauicles  arc  excited  into  adtion  by  diften- 
iion,  as  tbofe  of  the  rectum  and  biadder  are  induced  to  protrude 
their  contents  from  their  fenfe  of  the  ditlention,  rather  than 
of  the  acrimony  of  thofe  contents. 


There 


Sect.  XL  2.  SENSORIAL  ACTIONS. 


37 

There  are  other  obiedfs  adapted  to  ftimulate  the  nerves, 
which  terminate  in  a variety  of  membranes,  and  thofe  efpecial- 
ly  which  form  the  terminations  of  canals  : thus  the  prepara- 
tions of  mercury  particularly  afFedt  the  falivary  glands,  ipe- 
cacuanha affedfs  the  fphindter  of  the  anus,  cantharides  that  of 
the  bladder,  and  laftly,  every  gland  of  the  body  appears  to  be 
■induced  with  a kind  of  tafte,  by  which  it  (elects  or  forms  each 
its  peculiar  fluid  from  the  blood,  and  by  which  it  is  irritated 
into  adfivity. 

Many  of  thefe  external  properties  of  bodies,  which  ftimu- 
•late  our  organs  of  fenfe,  do  not  feem  to  affedf  this  by  a Angle 
impulfe,  but  by  repeated  impulfes ; as  the  nerve  of  the  ear  is 
probably  not  excitable  by  a (ingle  vibration  of  air,  nor  the 
optic  nerve  by  a Angle  particle  of  light ; which  circumftance 
produces  fome  analogy  between  thofe  two  fenfes,  at  the  fame 
rime  the  folidity  of  bodies  is  perceived  by  a Angle  application  ot 
a folid  body  to  the  nerves  of  touch,  and  that  even  through  the 
cuticle ; and  we  are  probably  pofiefled  of  a peculiar  fenfe  to 
diftinguifti  the  nice  degrees  of  heat  and  cold. 

The  fenfes  of  touch  and  of  hearing  acquaint  us  with  the  me- 
chanical impadf  and  vibration  of  bodies  ; thofe  of  fmell  and  tafte 
feem  to  acquaint  us  with  fome  of  their  chemical  properties ; 
while  the  fenfe  of  vifton  and  of  heat  acquaint  us  with  the  ex- 
iftence  of  their  peculiar  fluids. 

Senfation  and  Volition. 

II.  Many  motions  are  produced  by  pleafure  or  pain,  and 
that  even  in  contradidfion  to  the  power  of  volition,  as  in  laugh- 
ing or  in  the  ftranguary ; but  as  no  name  has  been  given  to 
pleafure  or  pain,  at  the  time  it  is  exerted  fo  as  to  caufe  Abrous 
motions,  we  have  ufed  the  term  fenfation  for  this  purpofe  ; and 
mean  it  to  bear  the  fame  analogy  to  pleafure  and  pain,  that  the 
word  volition  does  to  deAre  and  averfton. 

1.  It  was  mentioned  in  the  ftfth  Sedfion,  that  what  we  have 
termed  fenfation  is  a motion  of  the  central  parts,  or  of  the 
whole  fenlorium,  beginning  at  fome  of  the  extremities  of  it. 
This  appears,  ftrft,  becaufe  our  pains  and  pleafures  are  always 
caufed  by  our  ideas  or  mufcular  motions,  which  are  the  mo- 
tions of  the  extremities  of  the  fenforium,  And,  fecondly,  be- 
caufe the  fenfation  of  pleafure  or  pain  frequently  continues 
fome  time  after  the  ideas  or  mufcular  motions  which  excited 
it  have  ceafed : for  we  often  feel  a glow  of  pleafure  from  an 
agreeable  reverie,  for  many  minutes  after  die  ideas,  that  were 
the  fubjedt  of  it,  have  efcaped  our  memory , and  frequently  ex- 
perience 


SENSORIAL  ACTIONS.  Sect.  XI.  2. 


58 

perience  a dcjedfion  of  fpirits,  without  being  able  to  affign  the 
caule  of  it  but  by  much  recollection. 

When  the  fenforial  faculty  of  defire  or  averfion  is  exerted 
f®  as  to  caufe  fibrous  motions,  it  is  termed  volition ; which  is 
laid  in  Sedb.  V.  to  be  a motion  of  the  central  parts,  or  of  the 
whole  fenforium,  terminating  in  fome  of  the  extremities  of  it. 
This  appears,  firft,  becaufe  our  defires  and  averfions  always 
terminate  in  recolledting  and  comparing  our  ideas,  or  in  exert- 
ing our  mufcles  ; which  are  the  motions  of  the  extremities  of 
the  fenforium.  And,  fecondly,  becaule  delire  or  averlion  be- 
gins, and  frequently  continues  for  a time  in  the  central  parts  of 
the  fenforium,  before  it  is  peculiarly  exerted  at  the  extremities 
of  it ; for  we  fometimes  feel  defire  or  averfion  without  imme- 
diately knowing  their  objects,  and  in  ccnfequence  without  im- 
mediately exerting  any  of  our  mufcular  or  fenfual  motions  to 
attain  them:  as  in  the  beginning  of  the  paflion  of  love,  and 
perhaps  of  hunger,  or  in  the  ennui  of  indolent  people. 

Though  fenfation  and  volition  begin  or  terminate  at  the 
extremities  or  central  parts  of  the  fenforium.  yet  the  whole  of 
it  is  frequently  influenced  bv  the  exertion  of  thefe  faculties,  as 
appears  from  their  effects  on  the  external  habit ; for  the  whole 
Ikin  is  reddened  by  fhame,  and  an  univerfal  trembling  is  pro- 
duced by  fear  : and  every  mufcle  of  the  body  is  agitated  in  angry 
people  by  die  defire  of  revenge. 

There  is  another  very  curious  circumftanee,  which  flhews 
that  fenfation  and  volition  are  movements  of  the  fenforium  in 
contrary  directions ; that  is,  that  volition  begins  at  the  central 
parts  of  it,  and  proceeds  to  the  extremities;  and  that  fenfation 
begins  at  the  extremities,  and  proceeds  to  the  central  parts  : I 
mean,  that  thefe  two  fenforial  faculties  cannot  be  lirOngly  ex- 
erted at  the  fame  time ; for  when  we  exert  our  volit:  in  ftrongly, 
we  do  not  attend  to  nleaiure  or  pain ; and  converfely,  when 
we  are  ftrongly  affedbed  with  the  fenfation  of  pleafure  or  pain, 
we  ufe  no  volition — As  will  be  further  explained  in  Section 
XVIII.  on  fleep,  and  Section  XXXIV.  on  volition. 

2.  All  our  emotions  and  paflions  feem  to  arile  out  of  the 
exertions  of  thefe  two  faculties  of  the  animal  fenforium.  Price, 
hope,  joy,  are  the  names  of  particular  pleafures : fhame,  aef- 
pair,  forrow,  are  the  names  of  particular  pains : and  love,  am- 
bition, avarice,  of  particular  deiires : hatred,  difgufi,  fear,  anx- 
iety, of  particular  averfions.  Whilft  the  paflion  of  anger  in- 
cludes the  pain  from  a recent  injury,  and  the  averfion  to  the 
adverfary  that  occaiioned  it.  And  compaffion  is  the  pain  we 
experience  at  the  fight  of  mifery,  and  the  delire  of  relieving  it. 

There 


SENSORIAL  ACTIONS. 


Sect.  XI.  2. 


39 


There  is  another  tribe  of  defires,  which  are  commonly  termed 
appetites,  and  are  the  immediate  confequences  of  the  abfence  of 
fome  irritative  motions.  Thofe  which  arife  from  deleft  of  in- 
ternal irritations,  have  proper  names  conferred  upon  them,  as 
hunger,  thirft,  luft,  and  the  defre  of  air  when  our  refpiration 
is  impaired  by  noxious  vhpours ; and  of  warmth  when  we  are 
expoied  to  too  great  a degree  of  cold.  But  thofe,  whole  ft i- 
muli  are  external  to  the  body,  are  named  from  die  objefts 
which  are  by  nature  constituted  to  excite  them;  thefe  deftres 
originate  from  our  paft  experience  of  the  pleafurable  fenfaticns 
they  occaftcn,  as  the  fmell  of  an  hyacinth,  or  the  tafte  of  a 
pine-apple. 

Whence  it  appears,  that  our  pleafures  and  pains  are  at  leaf 
as  various  and  as  numerous  as  our  irritations ; and  that  our  de- 
ftres and  averftons  lnuft  be  as  numerous  as  our  pleafures  and 
pains.  And  that  as  fenfation  is  here  ufed  as  a general  terra 
tor  our  numerous  pleafures  and  pains,  when  they  produce  tire 
contractions  of  our  fibres ; fo  volition  is  the  general  name  for 
bur  deftres  and  averftons,  when  they  produce  fibrous  contrac- 
tions. Thus,  when  a motion  of  the  central  parts,  or  of  the 
whole  fenforium,  terminates  in  the  exertion  of  our  mufcles, 
it  is  generally  called  voluntary  aftion;  when  it  terminates 
in  the  exertion  of  our  ideas,  it  is  termed  recolleftion,  reafon- 
ing,  determining. 

3.  As  the  fenfations  of  pleafure  and  pain  are  originally  in- 
troduced by  the  irritations  of  external  objefts,  fo  our  deftres 
and  averftons  are  originally  introduced  by  thofe  fenfations ; for 
when  the  objects  of  our  pleafures  or  pains  are  at  a diftance, 
and  we  cannot  inftantaneoufiy  poffefs  the  one,  or  avoid  the 
other,  then  defire  or  averfion  is  produced,  and  a voluntary  ex- 
ertion of  our  ideas  or  mufcles  fucceeds. 

The  pain  of  hunger  extites  you  to  look  out  for  food;  the 
tree  that  {hades  you  prefents  its  odoriferous  fruit  before  your 
eyes ; you  approach,  pluck,  and  eat. 

The  various  movements  of  walking  to  the  tree,  gathering 
the  fruit,  and  maftic'ating  it,  are  affbeiated  motions  introduced 
by  their  connection  with  fenfation  ; but  ifi  from  the  uncom- 
mon height  ot  the  tree,  the  fruit  be  inacceffible,  and  you  are 
prevented  from  quickly  pofleffing  the  intended  pleafure,  defire 
is  produced.  The  confequence  of  this  defire  is,  firft,  a deli- 
beration about  the  means  to  gain  the  objedt  of  pleafure  in  pro- 
cels  ot  time,  as  it  cannot  be  procured  immediately  ; and,  iecond- 
ly,  the  mufeuiar  aftion  neceffary  for  this  purpofe. 

Y on  voluntarily  call  up  all  your  ideas  of  caufation,  that 
J ' are 


4C 


SENSORIAL  ACTIONS.  Sect.  XI.  3. 

are  related  to  the  effe£t  you  defire,  and  voluntarily  examine 
and  compare  fhem,  and  at  length  determine  whether  to  afcend 
the  tree,  or  to  gather  ftones  from  the  neighbouring  brook,  is 
eafier  to  praCtife,  or  more  promifing  of  fuccefs ; and,  finally, 
you  gather  the  ftones,  and  repeatedly  fling  them  to  diilodge  the 
fruit. 

Hence,  then,  we  gain  a criterion  to  diftinguifh  voluntary  acfts 
or  thoughts  from  thole  caufed  by  fenfation.  As  the  former 
are  always  employed  about  the  means  to  acquire  pleafui  able 
objects,  or  the  means  to  avoid  painful  ones ; while  the  latter 
are  employed  in  the  poiTtffion  of  thofe  which  are  already  in 
our  power. 

Hence  the  activity  of  this  power  of  volition  produces  tile 
great  difference  between  the  human  and  the  brute  creation. 
The  ideas  and  the  adtions  of  brutes  are  ahnoft  perpetually  em- 
ployed about  their  prefent  pleafures  or  their  prefent  pains ; and, 
except  in  the  few  inftances  which  are  mentioned  in  Sefb'on 
XVI.  cn  inftindt,  they  feldom  bufy  themfelves  about  the  means 
of  procuring  future  blifs,  or  of  avoiding  future  mifery;  fo  that 
the  acquiring  of  languages,  the  making  of  tools,  and  labouring 
for  money,  which  are  all  only  the  means  to  procure  pleafures, 
and  the  praying  to  the  Deity,  as  another  means  to  procure  hap- 
pinefs,  are  charadteriftic  of  human  nature. 

4.  As  there  are  many  difeafes  produced  by  the  quantity  of 
the  fenfation  of  pain  or  pleafure  being  too  great  or  too  little  ; fo 
are  there  difeafes  produced  bv  the  fufeeptibility  of  die  conftitu- 
tion  to  motions  caufable  by  thefe  fenlations  being  too  dull  or 
too  vivid.  This  fufeeptibility  ot  the  iyftem  to  feniitive  motions 
is  termed  fallibility,  to  diftinguifli  it  from  fenfation,  which  is 
the  adtual  exiftence  or  exertion  of  pain  or  pleafure. 

Other  claffes  of  difeafes  are  owing  to  the  exceffive  promp- 
titude or  fluggiflinefs  of  the  conftitution  to  voluntary  exertions, 
as  well  as  to  the  quantity  of  defire  or  of  averfion.  This  fuf- 
eeptibility of  the  fyftem  to  voluntary  motions  is  termed  volun- 
tarity,  to  diftinguifli  it  from  volition,  which  is  the  exertion  of 
defire  or  averfion  : theie  diieafes  will  be  treated  ot  at  length  in 
the  progrefs  of  the  work. 

AJfociation . 

III.  1.  It  is  not  eafy  to  afiign  a caufe,  why  thofe  animal 
movements  that  have  once  occurred  in  fucceffion,  or  in  com- 
bination, fhould  afterwards  have  a tendency  to  fucceed  or  ac- 
company each  other.  It  is  a property  of  animation,  and  diftin- 
guiihes  this  order  of  being  from  the  other  productions  of  nature. 

. Wheu 


Sect.  XII.  OF  STIMULUS  AND  EXERTION.  45 

When  a child  firft  wrote  the  word  man,  it  was  diftinguifh- 
ed  in  his  mind  into  three  letters,  and  thofe  letters  into  many 
parts  of  letters ; but  by  repeated  ufe  the  word  man  becomes  to 
his  hand  in  writing  it,  as  to  his  organs  of  fpeech  in  pronounc- 
ing it,  but  one  movement  without  any  deliberation,  or  fenfa- 
tion,  or  irritation,  interpofed  between  the  parts  of  it.  And  as 
many  feparate  motions  of  our  mufcles  thus  become  united,  and 
form,  as  it  were,  one  motion  ; fo  each  feparate  motion  before 
fuch  union,  may  be  conceived  to  confift  of  many  parts  or  fpa- 
ces  moved  through ; and  perhaps  even  the  individual  fibres  of 
our  mufcles  have  thus  gradually  been  brought  to  aCt  in  con- 
cert, which  habits  began  to  be  acquired  as  early  as  the  very 
formation  of  the  moving  organs,  long  before  the  nativity  of  the 
animal ; as  explained  in  SeCtiori  XVI.  2.  on  inftinCt. 

2.  There  are  many  motions  of  the  body,  belonging  to  the 
irritative  clafs,  which  might,  by  a hafty  obferver,  be  miftaken 
for  affociated  ones  ; as  the  periftaltic  motion  of  the  ftomach  and 
inteftines,  and  the  contractions  of  the  heart  and  arteries,  might 
be  fuppofed  to  be  affociated  with  the  irritative  motions  of  their 
nerves  of  fenfe,  rather  than  to  be  excited  by  the  irritation  of 
their  mufcular  fibres,  by  the  diftention,  acrimony,  or  momen- 
tum of  the  blood.  So  the  diftention  or  elongation  of  mufcles 
by  objeCts  external  to  them,  irritates  them  into  contraction, 
though  the  cuticle  or  other  parts  may  intervene  between  the 
ftimulating  body  and  the  contracting  mufcle.  Thus  a horfe 
voids  his  excrement  when  its  weight  or  bulk  irritates  the  rec- 
tum or  fphinCter  ani.  The  motion  of  thefe  mufcles  aCt  from 
the  irritation  of  diftention,  when  he  excludes  his  excrement; 
but  the  mufcles  of  the  abdomen  and  diaphragm  are  brought 
into  motion  by  affociation  with  thofe  of  the  fphinCter  and 
reCtum. 

SECT.  XII. 

OF  STIMULUS,  SENSORIAL  EXERTION,  AND  FI- 
BROUS CONTRACTION. 

I.  Of  fibrous  contraction.  1.  Two  particles  of  a fibre  cannot 
approach  without  the  intervention  of fomething,  as  in  mag - 
netifm,  electricity,  elafiicity.  Spirit  of  Ufe  is  not  eledric 
ether.  Galvan?  s experiments,  2.  Contraction  of  a fibre. 

3.  Relaxation fucceeds.  4.  Succefjive  contractions,  with 
intervals.  Quick  pulfe from  debility,  from  paucity  of  blood. 
W ?ak  contractions  peiformed  in  lefs  time , and  with  Jhorter 

intervals . 


42  OF  STIMULUS  AND  EXERTION.  Sect.  XIL 

intervals.  $.  Lafl  fituation  of  the  fibres  continues  after 
contrarian.  6.  Contrarian  greater  than  ufual  induces 
pleafure  or  pain.  J.  Mobility  of  the  fibres  uniform. 
Quantity  of  fenforial  -power  fluctuates.  Confliiutes  exci- 
tability. II.  Of  fenforial  exertion,  r.  Animal  motion  in- 
cludes fiimulus , fenforial  power,  and  contractile  fibres. 
The  fenfereial  faculties  aCt  feparately  or  conjointly.  Sti- 
mulus of  four  kinds.  Strength  and  weaknefs  defined. 
Senforial  power  perpetually  exhaufied  and  renewed. 
M^eaknefs  from  defied  of  fiimulus.  From  defeCt  of  fenfo- 
rial power,  the  direCt  and  indirect  debility  of  Dr.  Brown. 
Why  use  become  warm  in  Buxton  bath  after  a time , and 
fee  well  after  a time  in  a darkifh  room.  Fibres  may  ad 
violently,  or  with  their  whole  force,  and  yet  feebly.  Great 
exertion  m inflammation  explained.  Great  mufcular force 
of  fame  infane  people.  2.  Occafional  accumulation  of 
fenforial  power  in  mufcles  fubjedt  to  conflant  fiimulus.  In 
animals  fileeping  in  winter.  In  eggs,  feeds,  f chirr ous  tu- 
mours, tendons,  bones.  3,  Great  exertion  introduces 
pleafure  or  pain.  Inflammation.  Libration  of  the  fyf- 
tem  between  torpor  and  activity.  Fever-fits.  4.  Defire 
and  averfion  introduced.  Excefs  of  volition  cures  fevers. 
III.  Of  repeated  fiimulus.  I.  A fiimulus  repeated  too  fre- 
quently lofes  effeCt.  As  opium,  veins,  grief.  Hence  old 
age.  Opium  and  aloes  in  fmalt  aofes.  2.  A fiimulus  not 
repeated  too  frequently  does  not  lofe  effeCt _ Perpetual 
movement  of  the  vital  organs.  3.  A fiimulus  repeated 
at  uniform  times  produces  greater  effeCt.  Imtaiion  com- 
bined  with  affociation.  4.  A fiimulus  repeated frequently 
and  uniformly  may  be  withdrawn,  and  the  aCtion  of  the 
organ  will  continue.  Hence  the  bark  cures  agues,  and 
flrengthens  weak  conflitutions.  5.  DefeCt  of  fiimulus  re- 
peated at  certain  intervals  caufes  fever-fits.  6.  Stimu- 
lus long  applied  ceafcs  to  aCt  a fecond  time.  7.  If  a fii- 
mulus excites  Inflation  in  an  organ  not  uf  tally  excited 
into  Inflation,  inflammation  is  produced.  IV.  Ot  llimu- 
lus  greater  than  natural.  1.  A fiimulus  greater  than  na- 
tural diminifhes  the  quantity  of  fenforial  power 'in  gene- 
ral. 2.  In  particular  organs.  3.  Induces  the  organ  in- 
to [pa fnadic  aClions.  4.  Induces  the  antagonifi fibres  in- 
to Ciion.  C.  Induces  the  organ  into  convul/ive  or  fixed 
fpafns.  6.  Produces  paralyfis  of  the  organ.  V.  Ot  fti- 
mains  lefs  than  natural.  1.  Stimulus  lefs  than  natural 
occaflons  accumulation  of  fenforial  power  in  general.  2. 

In 


Sect.  XII.  i.  OF  STIMULUS  AND  EXERTION.  43 

In  particular  organs , JluJIhng  of  the  face  in  afrofly  morn- 
ing.  In  fibres  fubjeCt  to  perpetual  Jlimulus  only.  Quantity 
of  fenfor  ial  power  inverfely  as  the  ftmulus.  3.  Induces 
pain.  As  of  cold , hunger , head-ach.  4.  Induces  mere 
feeble  and  frequent  contraClioni  As  in  low  fevers. 
Which  are  frequently  owing  to  deficiency  of  fenforial 
power  rather  than  to  deficiency  of  Jhmulus.  5.  Inverts 
fuccejfive  trains  of  motion.  Inverts  ideas.  6.  Induces 
paralyfis  and  death.  VI.  Cure  of  increafed  exertion. 
1.  Natural  cure  of  exhauflion  of  fenforial  power.  2. 
Decreafe  the  irritations.  VaneJeCtion.  Cold.  Abfli - 
nence.  3.  Prevent  the  previous  cold  fit.  Opium.  Bark. 
Warmth.  Anger.  Surprife.  4.  Excite  Jome  other  part 
of  the  fy fern.  Opium  and  warm  bath  relieve  pains  both 
from  defedi  and  from  exceefs  of  Jlimulus.  5.  Firfl  in- 
creafe the  Jlimulus  above,  and  then  decreafe  it  beneath 
the  natural  quantity.  VII.  Cure  of  decreafed  exertion. 
I.  Natural  cure  by  accumulation  of  fenforial  power. 
Ague-fits.  Syncope.  2.  Increafe  the  Jlimulation,  by 
wine , opium,  given  fo  as  not  to  intoxicate.  Cheerful 
ideas.  3.  Change  the  kinds  of  Jlimulus.  4.  Stimulate 
the  ajfociated  organs.  Bliflers  of  ufe  in  heart-burn,  and. 
cold  extremities.  5.  Decreafe  the  jlimulation  for  a time , 
cold  bath.  6.  Decreafe  the  Jlimulation  below  natural , 
and,  then  increafe  it  above  natural.  Bark  after  emetics. 
Opium  after  vane fedtion.  Practice  of  Sydenham  in  chlo- 
rojis.  7.  Prevent  unneceffary  expenditure  of  fenforial 
power.  Decumbent  poflure,  Jilence,  darknefs.  Pulfe 
quickened  by  rifing  out  of  bed.  8.  To  the  greatef  degree 
of  quiefeence  apply  the  leaf  fimulus.  Otherwife  para- 
lyfis or  inflammation  of  the  organ  enfues.  Gin,  zvine , 
bliflers,  defray  by  too  great  Jlimulation  in  fevers  with  de- 
bility. Intoxication  in  the  flightefl  degree  fucceeded  by 
debility.  Golden  rule  for  determining  the  befl  degree  of 
Jlimulus  in  low  fevers.  Another  golden  rule  for  deter- 
mining the  quantity  of  fpirit  which  thofe  who  are  debili- 
taded  by  drinking  it  may  fafely  omit. 

I.  Of  fibrous  Contraction. 

1.  IF  two  particles  of  iron  lie  near  each  other,  without  mo- 
tion, and  afterwards  approach  each  other,  it  is  reafonable  to 
conclude  that  fomething  befides  the  iron  particles  is  the  caufe 
of  their  approximation;  this  invifible  fomething  is  termed 
magnetifm.  In  the  fame  manner,  if  the  particles  which  com- 
pofe  an  animal  raufcle  do  not  touch  each  other  in  the  relaxed 

H ftate 


44  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  r. 

Rate  of  the  mufcle,  and  are  brought  into  contaft  during  the 
contraftion  of  the  mufcle ; it  is  reafonable  to  conclude  that 
fome  other  agent  is  the  caufe  of  this  new  approximation. 
For  nothing  can  aft  where  it  does  not  exift ; for  to  aft  includes 
to  exift ; and  therefore  the  particles  of  the  mul'cular  fibre 
fwhich  in  its  ftate  of  relaxation  are  fuppofed  not  to  touch) 
cannot  affeft  each  other  without  the  influence  of  fome  inter- 
mediate agent ; this  agent  is  here  termed  the  fpirit  of  animation, 
or  fenforial  power,  but  may  with  equal  propriety  be  termed 
the  power  which  caufes  contraftion ; or  may  be  called  by  any 
other  name,  which  the  reader  may  choofe  to  affix  to  it. 

The  contraftion  of  a mufcular  fibre  may  be  compared  to 
the  following  eleftric  experiment,  which  is  here  mentioned,  not 
as  a philofophical  analogy,  but  as  an  iiluftration  or  fimile  to 
facilitate  the  conception  of  a difficult  fubjeft.  Let  twenty  very 
final!  Leyden  phials,  properly  coated,  be  hung  in  a row  by  fine 
fiik  threads,  at  a fmall  diftance  from  each  other;  let  the  in- 
ternal charge  of  c^ie  phial  be  pofitive,  and  of  the  other  nega- 
tive, alternately:  if  a communication  be  made  from  the  internal 
furface  of  the  firft  to  the  external  furface  of  the  laft  in  the  row, 
they  will  ail  of  them  inftantly  approach  each  other,  and  thus 
fhorten  a line  that  might  conneft  them  like  a mufcular  fibre.  See 
Botanic  Garden,  p.  i.  Canto  I.  1.  2C2,  note  onGymnotus. 

The  attractions  of  eleftric’ty  or  of  magnetifm  do  not  apply 
philofophically  to  the  iiluftration  of  the  contraftion  of  animal 
fibres,  fince  the  force  of-  thofe  attractions  increafes  in  fome 
proportion  inverfely  as  the  diftance ; but  in  mufcular  motion 
there  appears  no  difference,  in  velocity  or  ftrength,  during  the 
beginning  or  end  of  the  contraftion,  but  what  may  be  clearly 
aferibed  to  the  varying  mechanic  advantage  in  the  approxima- 
tion of  one  bone  to  another.  Nor  can  mufcular  motion  be 
affimilated,  with  greater  plaufability,  to  the  attraction  of  cohe- 
fion  or  elafticity  ; for  in  bending  a fteel  fpring,  as  a fmall  fword, 
a lefs  force  is  required  to  bend  k the  firft  inch  than'the  fecond  ; 
and  die  fecond  than  the  third;  the  particles  of  fteel  on  the  con- 
vex fide  of  the  bent  fpring  endeavouring  to  reftore  themfelves 
more  powerfully  the  further  they  are  drawn  from  each  other. 
See  Botanic  Garden,  p.  i.  addit.  note  XVIII. 

I am  aware  that  this  may  be  explained  another  way,  by  fup- 
ponng  the  elafticity  of  the  fpring  to  depend  more  on  the  com- 
preffion  of  the  particles  on  the  concave  fide,  than  on  the  exten- 
ftou  of  them  on  the  convex  lide ; and  by  fuppofing  the  elafticity 
of  the  elaftie  gum  to  depend  more  on  the  refiitance  to  the  late- 
ral compreffion  of  its  particles,  than  to  the  longitudinal  exten- 
iion  of  them.  Neverthelefs,  in  mufcular  contraftion,  as  above 

obferved. 


Sect. XII.  i.  OF  STIMULUS  AND  EXERTION.  45 

obferved,  there  appears  no  difference  in  the  velocity  or  force  of 
it  at  its  commencement  or  termination ; from  whence  we  muff 
conclude,  that  animal  contraction  is  governed  by  laws  of  its 
own,  and  not  by  thofe  of  mechanics,  chemiftry,  magnetifm,  or 
electricity. 

On  thefe  accounts  I do  not  think  the  experiments  conclufive, 
which  were  lately  publilhed  by  Galvani,  Volta,  and  ethers,  to 
fliew  a fimilitude  between  the  fpirit  of  animation,  which  con- 
tracts the  mufcular  fibres,  and  the  electric  fluid:  fence  the 
electric  fluid  may  act  only  as  a more  potent  ftimulus,  exciting 
the  mufcular  fibres  into  action,  and  not  by  fupplying  them  with 
a new  quantity  of  the  fpirit  of  life.  Thus,  in  a recent  hemi- 
plegia, I have  frequently  obferved,  when  the  patient  yawned  and 
ftretched  himfelf,  that  the  paralytic  limbs  moved  alfo,  though 
•they  were  totally  difobedient  to  the  will.  And  when  he  was 
.electrified,  by  palling  fhocks  from  the  affected  hand  to  the  af- 
fected foot,  a motion  of  the  paralytic  limbs  was  alio  pVoduced. 
Now,  as  in  the  act  of  yawning  the  mufcles  of  the  paralytic  limbs 
were  excited  into  action  by  the  ftimulus  of  the  irktomenefs  of 
4 continued  pofture,  and  not  by  an  additional  quantity  of  the 
fpirit  of  life;  fo  we  may  conclude,  that  the  paftage  of  the  elec- 
tric fluid,  which  produced  a fimilar  effect,  acted  only  as  a fti- 
mulus,  and  not  by  fupplying  any  addition  of  fenfonal  power. 

If,  neverthelefs,  this  theory  Ihould  ever  become  eftablifhed,  a 
ftimulus  mull  be  called  an  eductor  of  vital  ether ; which  ftimu- 
lus may  confift  of  fenfation  or  volition,  as  in  the  electric  eel, 
as  well  as  in  the  appulfes  of  external  bodies ; and,  by  drawing 
off  the  charges  of  vital  fluid,  may  occafion  the  contraction  or 
motions  of  the  mufcular  fibres  and  organs  of  l'enfe. 

2.  The  immediate  effect  of  the  action  of  the  fpirit  of  anima- 
tion, or  fenforial  power,  on  the  fibrous  parts  of  the  body,  whe- 
ther it  acts  in  the  mode  of  irritation,  fenfation,  volition,  or  af- 
fociatiou,  is  a , contraction  of  the  animal  fibre,  according  to  the 
fecond  law  of  animal  caufation.  Sect.  IV.  Thus  the  fti- 
mulus  of  the  blood  induces  the  contraction  of  the  heart ; the 
agreeable  tafte  of  a ftrawberry  produces  the  contraction  of 
the  mufcles  of  deglutition ; the  effort  of  the  will  contracts 
the  mufcles  which  move  the  limbs  in  walking ; and,  by  affoci- 
ation,  other  mufcles  of  the  trunk  are  brought  into  contraction 
to  preferve  the  balance  of  the  body.  The  fibrous  extremities 
of  the  organs  ot  fenfe  have  been  {hewn,  by  the  ocular  fpectra 
in  Sect.  III.  to  fuffer  fimilar  contraction  by  each  of  the  above 
modes  of  excitation;  and  by  their  configurations  to  conftitute 
our  ideas. 

3.  After  animal  fibres  have  for  fome  time  been  excited  into 

contraction, 


46  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  1. 

contraction,  a relaxation  fucceeds,  even  though  the  exciting 
caufe  continues  to  at.  In  refpect  to  the  irritative  motions, 
this  is  exemplified  in  the  periftaltic  contractions  of  the  bow- 
els; which  ceafe  and  are  renewed  alternately,  though  the  fti- 
mulus  of  the  aliment  continues  to  be  uniformly  applied  -}  in  the 
fenfitive  motions,  as  in  ftrangury,  tenefmus,  and  parturition, 
the  alternate  contractions  and  relaxations  of  the  mufcles  exift, 
though  the  ftimulus  is  perpetual.  In  our  voluntary  exertions 
it  is  experienced,  as  no  one  can  hang  long  by  the  hands,  how- 
ever vehemently  he  wills  fo  to  do ; and  in  the  aflfociate  motions* 
the  conftant  change  of  our  attitudes  evinces  the  necefiity  of  re- 
laxation to  thofe  mufcles  which  have  been  long  in  action. 

This  relaxation  of  a mufcle,  after  its  contraction,  even  though 
the  ftimulus  continues  to  be  applied,  appears  to  ariie  from  the 
expenditure  or  diminution  of  the  fpirit  of  animation  previoufly 
refident  in  the  mufcle,  according  to  the  feccnd  lave’  of  animal 
caufation  in  Set.  IV.  In  thofe  conftitutions  which  are  termed 
weak,  the  fpirit  of  animation  becomes  fooner  exhaufted,  and 
tremulous  motions  are  produced,  as  in  the  hands  of  infirm  peo- 
ple, when  they  lift  up  a cup  to  their  mouths.  This  quicker 
exhauftion  of  the  fpirit  of  animation  is  probably  owing  to  a 
lefs  quantity  of  it  refiding  in  the  ’a ting  fibres,  which  therefore 
more  frequently  require  a fupply  from  the  nerves  which  be- 
long to  them. 

4.  If  the  fenforial  power  continues  to  at,  whether  it  ats 
in  the  mode  of  irritation,  fenfation,  volition,  or  affociation,  a 
new  contration  of  the  animal  fibfe  fucceeds  after  a certain 
interval  ; which  interval  is  of  fhorter  continuance  in  weak 
people  than  in  ftrong  ones.  This  is  exemplified  in  the  fhak- 
ing  of  the  hands  of  weak  people,  when  they  attempt  to  write. 
In  a manufeript  epiftle  of  one  of  my  correfpondents,  which  is 
written  in  a fmall  hand,  I obferved  from  four  to  fix  zigzags  in 
the  perpendicular  ftroke  of  every  letter,  which  fhews  that  both 
the  contractions  of  the  fingers,  and  intervals  between  them, 
rnuft  have  been  performed  in  very  fhort  periods  of  time. 

The  times  of  contraction  of  the  mufcles  of  enfeebled  people 
being  lefs,  and  the  intervals  between  thofe  contractions  being 
lefs  alfo,  accounts  for  the  quick  pulfe  in  fevers  with  debility, 
and  in  dying  animals.  The  fliortnefs  of  the  intervals  between 
one  contraction  and  another  in  weak  conftitutions,  is  pro- 
bably owing  to  the  general  deficiency  of  the  quantity  of  the 
fpirit  of  animation,  and  therefore  there  is  a lefs  quantity  ot 
it  to  be  teceived  at  each  interval  of  the  activity  of  the  fibres. 
Hence,  in  repeated  motions,  as  of  the  fingers  in  performing  on 
the  harpfichord,  it  would  at  firft  fight  appear,  that  fwiftnefs 


Sect. XII.  i.  OF  STIMULUS  AND  EXERTION.  47 

and  ftrength  are  incompatible ; neverthelefs,  the  Angle  contrac- 
tion of  a mufcle  is  performed  with  greater  velocity,  as  well  as 
with  greater  force,  by  vigorous  conllitutions,  as  in  throwing  a 
javelin. 

There  is,  however,  another  circumftance,  which  may  often 
contribute  to  eaufe  the  quicknefs  of  the  pulie  in  nervous  fe- 
vers, as  in  animals  bleeding  to  death  in  the  flaughter-boufe, 
which  is  the  deficient  quantity  of  blood ; whence  the  heart  is 
but  half  diftended,  and  in  confequence  fooner  contrads.  See 
Sed.  XXXII.  2.  1. 

For  we  muft  not  confound  frequency  of  repetition  with 
quicknefs  of  motion,  or  the  number  of  pulfations  with  the 
velocity,  with  which  the  fibres,  which  conftitute  the  coats  of 
the  arteries,  contrad  themfelves.  For  where  the  frequency 
of  the  pulfations  is  but  feventy-five  in  a minute,  as  in  health; 
the  contrading  libres,  which  conftitute  the  fides  of  the  arteries, 
may  move  through  a greater  fpace  in  a given  time,  than  where 
the  frequency  of  pulfation  is  one  hundred  and  fifty  in  a minute, 
as  in  feme  fevers  with  great  debility.  For  if  in  thofe  fevers 
the  arteries  do  not  expand  themfelves  in  their  diaftole  to  more 
than  half  the  ufual  diameter  of  their  diaftole  in  health,  the  fibres 
which  conftitute  their  coats  will  move  thiough  a lefs  fpace  in 
a minute  than  in  health,  though  they  make  two  pulfations  for 
one. 

Suppofe  the  diameter  of  the  artery  during  its  fyftole  to  be 
one  line,  and  that  the  diameter  of  the  fame  artery  during  its 
diaftole,  in  health,  is  four  lines,  and  in  a fever,  with  great  debi- 
lity, is  only  two  lines — It  follow^,  that  the  arterial  fibres  con- 
trad,  in  health,  from  a circle  of  twelve  lines  in  circumference 
to  a circle  of  three  lines  in  circumference ; that  is,  they  move 
through  a fpace  of  nine  lines  in  length  ; while  the  arterial  fibres 
in  the  fever,  with  debility,  would  twice  contrad  from  a circle 
of  fix  lines,  to  a circle  of  three  lines ; that  is,  while  they  move 
through  a fpace  equal  to  fix  lines.  Hence,  though  the  fre- 
quency- of  pulfation  in  fever  be  greater,  as  two  to  one,  yet  the 
velocity  of  contradion  in  health  is  greater,  as  nine  to  fix,  or 
as  three  to  two. 

On  the  contrary,  in  inflammatory  difeafes  wdth  ftrength,  as 
in  the  pleurify,  the  velocity  of  the  contrading  fides  of  the  arte- 
ries is  much  greater  than  in  health ; for  if  we  fuppofe  the 
number  of  pulfations  in  a pleurify  to  be  half  as  much  more 
than  in  health ; that  is,  one  hundred  and  twenty  to  eighty, 
(which  is  about  what  generally  happens  in  inflammatory  dif- 
eafes) and  if  the  diameter  of  the  artery  in  diaftole  be  one  third 
greater  than  in  hcplth,  which  I believe  is  near  the  truth,  the 
' refult 


48  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  j. 

refult  will  be,  that  the  velocity  of  the  contractile  Tides  of  the  ar- 
teries will  be  in  a pleurify,  as  two  and  an  half  to  one,  compar- 
ed to  the  velocity  of  their  contraction  in  a ftate  of  health ; 
for  if  the  circumference  of  the  fyftole  of  the  artery  be  three 
lines,  and  the  diaftole  in  health  be  twelve  lines  in  circumfe- 
rence, and  in  a pleurify  eighteen  lines  ; and  fecondly,  if  the  ar- 
tery pulfates  thrice  in  the  difeafed  ftate  for  twice  in  the  healthv 
one,  it  follows,  that  the  velocity  of  contraction  in  die  difeafed 
ftate  to  that  in  the  healthy  ftate,  will  be  forty-five  to  eighteen, 
or  as  two  and  a half  to  one. 

From  hence  it  would  appear,  that  if  we  had  a criterion  to 
determine  the  velocity  of  the  arterial  contractions,  it  would  at 
the  fame  time  give  us  their  ftrength,  and  thus  be  of  more  fer- 
vicein  diftinguiihingdifeafes,  than  the  knowledge  of  their  fre- 
quency. As  fuch  a criterion  cannot  be  had,  the  frequency  of 
pulfation,  the  age  of  the  patient  being  allowed  for,  will  infome 
meafure  alfift  us  to  diftinguifli  arterial  ftrength  from  arterial 
debility;  fince,  in  inflammatory  difeafes,  with  ftrength,  the  fre- 
quency feldom  exceeds  one  hundred  and  eighteen,  or  one  hun- 
dred and  twenty  pulfations  in  a minute,  unlefs  under  peculiar 
circumftances,  as  the  great  additional  ftimuli  of  wine  or  of 
external  heat. 

5.  After  a mufcle  or  organ  of  fenfe  has  been  excited  into 
conti  adlion,  and  the  fenforial  power  ceafes  to  adt,  the  laft  litu- 
htion  or  configuration  of  it  continues,  unlefs  it  be  difturbed  by 
the  adlion  of  lome  antagonift  fibres,  or  other  extraneous 
power.  Thus,  in  weak  or  languid  people,  wherever  they 
throw  their  limbs  on  their  bed  or  fofa,  there  thev  lie,  till  ano- 
ther exertion  changes  their  attitude;  hence  one  kind  of  ocular 
fpedtra  feems  to  be  produced  after  looking  at  bright  objedts : 
thus,  when  a fire-ftick  is  whirled  round  in  the  night,  there  ap- 
pears in  the  eye  a complete  circle  of  fire,  the  adlion  or  configu- 
ration of  one  pare  of  the  retina  not  ceafing  before  the  return 
of  the  whirling  fire. 

Thus,  if  any  one  looks  at  the  fetting  fun  for  a fliort  time, 
and  then  covers  his  clofed  eyes  with  his  hand,  he  will,  tor  many 
feconds  of  time,  perceive  the  image  of  the  fun  on  his  retina. 
A funilar  image  of  all  other  bodies  would  remain  l'ome  time 
in  the  eye,  but  is  effaced  by  the  eternal  change  of  the  motions 
of  the  extremity  of  this  nerve  in  our  attention  to  other  objedts. 
See  Sedt.  XVII.  1.  3.  on  fleep.  Hence  the  dark  l'pots,  and 
other  ocular  fpedtra,  are  more  frequently  attended  to,  and  re- 
main longer  in  the  eyes  of  weak  people,  as  after  violent  exer- 
cife,  intoxication,  or  want  of  fleep. 

6.  A contradtion  of  the  fibres  fomewhat  greater  than  ufual, 

introduces 


Sect.  XII.  i.  OF  STIMULUS  AND  EXERTION.  49 

introduces  pleafurable  fenfation  into  the  fyftem,  according  to 
the  fourth  law  of  animal  caufation.  Lienee  the  pleafure  in 
the  beginning  of  drunkennefs  is  owing  to  the  increafed  adfion 
of  the  fyftem  from  the  ftimulus  of  vinous  fpirit,  or  of  opium. 
If  the  contractions  be  ftill  greater  in  energy  or  duration,  pain- 
ful fenfations  are  introduced,  as  in  confequence  of  great  heat, 
or  cauftic  applications,  or  fatigue. 

If  any  part  of  the  fyftem,  which  is  ufed  to  perpetual  ac- 
tivity, as  the  ftomach,  or  heart,  or  the  fine  veflels  of  the  fkin, 
adds  for  a time  with  lefs  energy,  another  kind  of  painful  fen- 
fation enfues,  which  is  called  hunger,  or  faintnefs,  or  cold. 
This  occurs  in  a lefs  degree  in  the  locomotive  mulcles,  and  is 
called  wearifomenefs.  In  the  tw.o  former  kinds  of  fenfation 
there  is  an  expenditure  of  fenforial  power  ; in  thefe  latter  there 
is  an  accumulation  of  it. 

7.  We  have  ufed  the  words  exertion  of  fenforial  power  as 
a general  term  to  exprefs  either  irritation,  fenfation,  volition, 
or  afiociation ; that  is,  to  exprefs  the  activity  or  motion  of  the 
fpirit  of  animation,  at  the  time  it  produces  the  contractions  of 
the  fibrous  parts  of  the  fyftem.  It  may  be  fuppofed  that'  there 
may  exift  a greater  or  lefs  mobility  of  the  fibrous  parts  of  our 
fyftem,  or  a propenfity  to  be  ftimulated  into  contraction  by 
the  greater  or  lefs  quanti  ty  or  energy  of  the  fpirit  of  animation ; 
and  that  hence,  if  the  exertion  of  the  fenforial  power  be  in 
its  natural  ftate,  and  the  mobility  of  the  fibres  be  increafed,' 
the  fame  quantity  of  fibrous  contractions  will  be  caufed,  as  if 
the  mobility  of  the  fibres  continues  in  its  natural  ftate,  and 
the  fenforial  exertion  be  increafed. 

Thus  it  may  be  conceived,  that  in  difeafes  accompanied  with 
ftrength,  as  in  inflammatory  fevers,  with  arterial  ftrength,  that 
the  caufe  of  greater  fibrous  contradfion  may  exift  in  the  in- 
creafed mobility  of  the  fibres,  whofe  contradlions  are  thence 
both  more  forcible  and  more  frequent.  And  that  in  difeafes 
attended  with  debility,  as  in  nervous  fevers,  where  the  fibrous 
contradlions  are  weaker  and  more  frequent,  it  may  be  con- 
ceived that  the  caufe  confifts  in  a decreafe  of  mobility  of  the 
fibres;  and  that  thofe  weak  conftitutions,  which  are  attended 
with  cold  extremities  and  large  pupils  of  the  eyes,  may  pofiefs 
lefs  mobility  of  the  contradfiie  fibres,  as  well  as  lefs  quantity  of 
exertion  of  the  fpirit  of  animation. 

In  anfwer  to  this  mode  of  reafoning,  it  may  be  fufficient  to 
obferve,  that  the  contradfiie  fibres  conlift  of  inert  matter ; and 
when  the  fenforial  power  is  withdrawn,  as  in  death,  they  pofiefs 
no  power  of  motion  at  all,  but  remain  in  their  laft  ftate,  whe- 
ther of  contradfion  or  relaxation,  and  muff  thence  derive  the 

whole 


50  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  x. 

whole  of  this  property  from  the  fpirit  of  animation.  At  the 
fame  time  it  is  not  improbable,  that  the  moving  fibres  of  ftrong 
people  may  po fiefs  a capability  of  receiving  or  containing  a 
greater  quantity  of  the  fpirit  of  animation  than  thofe  of  weak 
people. 

In  every  contraction  of  a fibre  there  is  an  expenditure  of 
the  fenforial  power,  or  fpirit  of  animation  ; and  where  the  ex- 
ertion of  this  fenforial  power  has  been  for  fome  time  increaf- 
ed,  and  the  mufcles  or  organs  of  fenfe  have  in  confequence 
added  with  greater  energy,  its  propenlity  to  activity  is  propor- 
tionally leflened;  which  is  to  be  afcribed  to  the  exhauftion  or 
diminution  of  its  quantity.  On  the  contrary,  where  there 
has  been  lefs  fibrous  contraction  than  ufual  for  a certain  time, 
the  fenforial  power,  or  fpirit  of  animation,  becomes  accumu- 
lated in  the  inactive  part*of  the  fyftem.  Hence  vigour  fuc- 
ceeds  reft ; and  hence  the  propenfity  to  action,  of  all  our  or- 
gans of  fenfe  and  mufcles,  is  in  a ftate  of  perpetual  fluctuation. 
The  irritability,  for  inftance,  of  the  retina;  that  is,  its  quan- 
tity of  fenforial  power,  varies  every  moment,  according  to  the 
hriglftnefs  orobfcurit.y  of  the  object  laft  beheld,  compared  with 
the  prefent  one.  The  fame  occurs  to  our  fenfe  ot  heat,  and 
to  every  part  of  our  fyftem,  which  is  capable  of  being  excited 
into  action. 

When  this  variation  of  the  exertion  of  the  fenforial  power 
becomes  much  and  permanently  above  or  beneath  the  natural 
quantity,  it  becomes  a difeafe.  It  the  irritative  motions  be  too 
great  or  too  little,  it  thews  that  the  ftimulus  of  external  things 
afledls  this  fenforial  power  too  violently  or  too  inertly.  It  the 
fenfitive  motions  be  too  great  or  too  little,  the  caule  arifes  from 
the  deficient  or  exuberent  quantity  of  fenfation  produced  in 
confequence  of  the  motions  of  the  mufcular  fibres  or  organs  of 
fenfe.  If  the  voluntary  acftions  are  diteafed,  the  caufe  is  to  be 
looked  for  in  the  quantity  of  volition  produced,  in  confequence 
of  the  defire  or  averfion  occafioned  by  the  painful  or  pleafur- 
able  fenfations  above  mentioned.  And  the  difeafes  of  afloci- 
ations  probably  depend  on  the  greater  or  lets  quantity  of  the 
other  three  fenforial  powers  by  which  they  were  formed. 

From  whence  it  appears,  that  the  propenfity  to  action,  whe- 
ther it  be  called  irritability,  fenfibility,  voluntarily,  or  afloci- 
abilitv,  is  only  another  mode  of  expreflion  for  the  quantity  of 
fenforial  power,  refining  in  the  organ,  to  be  excited.  And  that, 
on  the  contrary,  the  words  irritability  and  infenfibiliry,  toge- 
ther with  inaptitude  to  voluntary  and  aflociate  motions,  are 
fynoniinous  with  deficiency  of  the  quantity  of  fenforial  power, 
or  of  the  fpirit  of  animation,  reliding  in  the  organs  to  be  ex- 
cited. 


Sect.  XII.2.  OF  STIMULUS  AND  EXERTION.  51 


II.  Of  fenforial  Exertion. 

1 . There  are  three  circumftances  to  be  attended  to  in  the  pro- 
duction of  animal  motions.  I ft.  The  ftimulus.  2d.  The 
fenforial  power.  3d.  The  contraClile  fibre. — 1 ft.  A ftimu- 
lus, external  to  the  organ,  originally  induces  into  aCtion  the 
fenforial  faculty  termed  irritation;  this  produces  the  contrac- 
tion of  the  fibres,  which,  if  it  be  perceived  at  all,  introduces 
pleafure  or  pain  ; which,  in  their  aCtive  ftate,  are  termed  fen- 
fation, which  is  another  fenforial  faculty,  and,  occafionally 
produces  contraction  of  the  fibres : this  pleafure  or  pain  is 
therefore  to  be  confidered  as  another  ftimulus,  which  may 
either  aCt  alone  or  in  conjunction  with  the  former  faculty  of 
the  fenforium,  termed  irritation.  This  new  ftimulus  of  plea- 
fure or  pain  either  induces  into  aCtion  the  fenforial  faculty, 
termed  fenfation,  which  then  produces  the  contraction  of  the 
fibres ; or  it  introduces  defire  or  aveffion,  which  excite  into 
aCtion  another  fenforial  faculty,  termed  volition,  and  may 
therefore  be  confidered  as  another  ftimulus,  which  either  alone, 
or  in  conjunction  with  one  or  both  ot  the  two  former  facul- 
ties of  the  fenforium,  produces  the  contraction  of  animal  fibres. 
There  is  another  fenforial  power,  that  of  aftbciation,  which 
perpetually,  in  conjuCtion  with  one  or  more  of  the  above,  and 
frequently  fingly,  produces  the  contraction  ot  animal  fibres, 
and  which  is  itielf  excited  into  aCtion  by  the  previous  motions 
of  contracting  fibres. 

Now,  as  the  fenforial  power,  termed  irritation,  refiding  in 
any  particular  fibres,  is  excited  into  exertion  by  the  ftimulus 
of  external  bodies  aCting  on  tliofe  fibres  ; the  fenforial  power, 
termed  fenfation,  refiding  in  any  particular  fibres,  is' excited 
into  exertion  by  the  ftimulus  of  pleafure  or  pain  aCting  on 
thofe  fibres ; the  fenforial  power,  termed  volition,  refiding  in 
any  particular  fibres,  is  excited  into  exertion  by  the  ftimulus 
of  defire  or  averfion;  and  the  fenforial  power,  termed  affoci- 
ation,  refiding  in  any  particular  fibres,  is  excited  into  aCtion 
by  the  ftimulus  of  other  fibrous  motions,  which  had  frequent- 
ly preceded  them.  The  word  ftimulus  may  therefore  be  ufed, 
without  impropriety  of  language,  for  any  of  thefe  four  Caufes, 
which  excite  the  four  fenforial  powers  into  exertion.  For 
though  the  immediate,  caufe  of  volition  has  generally  been 
termed  a motive , and  that  of  irritation  only,  has  generally  ob- 
tained the  name  of  Jiimulus ; yet,  as  the  immediate  caufe 
which  excites  the  fenforial  powers  of  fenfation,  or  of  aflocia- 
tion,  into  exertion,  have  obtained  no  general  name,  we  {hall 
ufe  the  word  ftimulus  for  them  all. 

I 


Hence 


5a  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  2: 

Hence  the  quantity  of  motion  produced. in  any  particula 
part  of  the  animal  iyftem,  will  be  as  the  quantify  of  ltimulus 
and  the  quantity  of  fenforial  power,  or  fpirit  of  animation,  te- 
nding in  the  contracting  fibres.  Where  both  thefe  quantities 
are  great ,jlrength  is  produced,  when  that  word  is  applied  to 
the  motions  ot  animal  bodies.  Where  either  of  them  is  defi- 
cient, weaknefs  is  produced,  as  applied  to  the  motions  of  ani- 
mal bodies. 

Now,  as  the  fenforial  power,  or  fpirit  of  animation,  is  per- 
petually exbaufted  by  the  expenditure  of  it  in  fibrous  contrac- 
tions, and  rs  perpetually  renewed  by  the  fecretion  or  produc- 
tion of  it  in  the  brain  and  fpinal  mar  row,  the  quantity  of  ani- 
mal ftrength  mud  be  in  a perpetual  ftate  of  fluctuation  on  this 
account ; and  if  to  this  be  added  tire  unceafrng  variation  of  all 
the  four  kinds  of  ftimulus  above  deferibed,  which  produce  the 
exertion  of  the  fenforial  powers,  the  ceafelefs  viciffitude  of 
animal  ftrength  becomes  ealily  comprehended. 

If  the  quantity  of  fenforial  power  remains  the  fame,  and  the 
quantity  of  flimulus  be  leflened,  a weaknefs  of  the  fibrous  con- 
tractions eniues,  w'hich  may  be  denominated  debility  from 
dcfctl  of  f imulus.  If  the  quantity  of  flimulus  remains  the 
fame,  and  die  quantity  of  fenforial  power  be  leftened,  anodier 
kind  of  weaknefs  eniues,  which  may  be  termed  debility  from 
defett  of  fenforial  power ; the  tonner  of  thefe  is  called  by  Dr. 
Brown,  in  his  Elements  of  Medicine,  diredt  debility,  and  the 
latter  indirect  debility.  The  coincidence  ofTome  parts  of  tin's 
work,  with  correfpondent  deductions  in  die  Brunonian  Ele- 
menta  Medicina,  a werk  (with  fome  exceptions)  of  great  ge- 
nius, muft  be  confidered  as  confirmations  of  the  truth  of  the 
theory,  as  diey  were  probably  arrived  at  by  different  trains  of 
reafoning. 

Thus,  in  thofe  who  have  been  expofed  to  cold  and  hunger, 
there  is  a deficiency  ot  ftimulus.  While  in  nervous  fever 
there  is  a deficiency  of  fenforial  power : and  in  habitual  drunk- 
ards, in  a morning  before  their  ulual  potation,  there  is  a defi- 
ciency both  ot  ftimulus  and  of  fenforial  power ; while,  on  the 
other  hand,  in  the  beginning  of  intoxication,  there  is  an  excefs 
of  ftimulus:  in  the  hot  ach,  after  the  hands  have  been  immerf- 
ed  in  fnow,  there  is  a redundancy  of  fenforial  power;  and  in 
inflammatory  difeafes  w ith  arterial  ftrength,  there  is  an  excels 
of  both. 

Hence,  if  the  fenforial  power  be  leffened,  while  the  quantity 
of  ftimulus  remains  the  fame  as  in  nervous  fever,  the  frequen- 
cy of  repetition  of  the  arterial  contractions  mav  continue ; but 
their  lotcc.  in  relpect  to  removing  obltacles,  as  in  promoting 

the 


Sect.  XII.  2.  GF  STIMULUS  AND  EXERTION.  53 

the  circulation  of  the  blood,  or  the  velocity  of  each  contradtion, 
will  be  diminifhed ; that  is,  the  animal  {Length  will  be  leflened. 
And,  fecondly,  if  the  quantity  of  fenforial  power  be  lefiened, 
and  the  ftimulus  be  increafed  to  a certain  degree,  as  in  giving 
opium  in  nervous  fevers,  the  arterial  contradfions  may  be 
performed  more  frequently  than  natural,  yet  with  lefs  {Length. 

And  thirdly,. if  the  fenforial  power  continues  the  fame  in 
refpedt  to  quantity,  and  the  ftimulus  be  fomewhat  diminifhed, 
as  in  going  into  a darkifh  room,  or  into  a coldifh  bath,  lup- 
pofe  of  about  eighty  degrees  of  heat,  as  Buxton-bath,  a tem- 
porary weaknefs  of  the  affedfed  fibres  is  induced,  till  an  accu- 
mu.ation  of  fenforial  power  gradually  fucceeds,  and  counter- 
balances the  deficiency  of  ftimulus  ; and  then  the  bath  ceafes 
to  feel  cold,  and  the  room  ceales  to  appear  dark;  becaufe  the 
fibres  of  the  fubcutaneous  v-effels,  or  of  the  organs  of  feilfe, 
adf  with  their  ufual  energy. 

A .fet  of  mufcular  fibres  may  thus  be  ftimulated  into  violent 
exertion;  that  is,  they  may  act  frequently,  and  with  their 
whole  fenforial  power,  but  may  neverthelels  not  adf  ftrongly; 
becaufe  the  quantity  of  their  fenforial  power  was  originally 
fmall,  or  was  previoufty  exhaufted.  Hence  a ftimulus  may 
he  great,  and  the  irritation  in  confequence  adf  with  its  full 
force,  as  in  the  hot  paroxyfms  of  nervous  fever;  but  if  the 
fenforial  power,  termed  irritation,  be  fmall  in  quantity,  the 
force  of  the  fibrous  contradfions,  and  the  times  of  their 
continuance  in  theli*  con-'Tadted  ftate,  will  be  proportionally 
final!. 

In  the  fame  manner,  in  the  hot  paroxyfm  of  putrid  fevers, 
which  are  fhewn  in  Sedt.  XXXIII.  to  be  inflammatory  fe- 
vers, with  arterial  debility,  the  fenforial  power,  termed  fenfa- 
tion,  is  exerted  with  great  adlivity ; yet  the  fibrous  contrac- 
tions, which  produce  the  circulation  of  the  blood,  are  perform- 
ed without  {Length,  becaufe  the  quantity  of  fenforial  power, 
then  refiding  in  that  part  of  the  fyftem,  is  fmall. 

Thus,  in  irritative  fever,  with  arterial  ftrength,  that  is,  with 
excefs  of  fpirit  of  animation,  the  quantity  of  exertion  during 
the  hot  part  of  the  paroxyfm,  is  to  be  eftimated  from  the  quan- 
tity of  ftimulus,  and  the  quantity  of  fenforial  powrer;  while 
in  fenfttive  (or  inflammatory)  lever,  with  arterial  ftrength, 
that  is,  with  excefs  of  fpirit  of  animation,  the  violent  and  for- 
cible adtions  of  the  vafcular  fyftem,  during  the  hot  part  of  the 
paroxyfm,  are  induced  by  the  exertions  of  two  fenforial 
powers,  which  are  excited  by  two  kinds  of  ftimulus.  Thele 
are  the  fenforial  power  of  irritation,  excited  by  the  ftimulus  of 
bodies  external  to  the  moving  fibres,  and  the  fenforial  power- 

ot 


54  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  2. 


of  fenfation,  excited  by  the  pain  in  confequence  of  the  increafed 
contractions  of  thofe  moving  fibres. 

And  in  infane  people,  in  fome  cafes,  the  force  of  their  muf- 
cular adtions  will  be  in  proportion  to  the  quantity  of  fenforial 
power  which  they  poffefs,  and  the  quantity  of  the  ftimulus  of 
defire  or  averfion  which  excites  their  volition  into  aCtion. 
At  the  fame  time,  in  other  cafes,  the  ftimulus  of  pain  or  plea- 
fure,  and  the  ftimulus  of  external  bodies,  may  excite  into  ac- 
tion the  fenforial  powers  ot  fenfation  and  irritation,  and  thus 
add  greater  force  to  their  mufcular  adtions. 

2.  The  application  of  the  ftimulus,  whether  that  ftimulus 
be  fome  quality  of  external  bodies,  or  pleafure  or  pain,  or  de- 
fire  or  averfion,  or  a link  of  affociation,  excites  the  corrcf- 
pondent  fenforial  power  into  action,  and  this  caufes  the  con- 
traction of  the  libre.  On  the  contraction  of  the  fibre,  a part 
of  the  fpirit  of  animation  becomes  expended,  and  the  fibre  ccai'es 
to  contraCt,  though  the  ftimulus  continues  to  be  applied,  till, 
in  a certain  time,  the  fibre  having  received  a lupply  of  fenfo- 
rial power,  is  ready  to  contract  again,  it  the  ftimulus  conti- 
nues to  be  applied.  If  the  ftimulus,  on  the  contrary,  be  with- 
drawn, the  fame  quantity  of  quiefeent  fenforial  power  becomes 
reiident  in  the  fibre  as  before  its  contraction ; as  appears  from 
the  readinefs  for  aCtion  of  the  large  locomotive  mufcles  ot  the 
body,  in  a fhort  time  after  common  exertion. 


But  in  thofe  mufcular  fibres  which  are  lubjeCt  to  conftant 
ftimulus,  as  the  arteries,  glands,  and  capillary  vefiels,  another 
phenomenon  occurs,  if  their  aecuftomed  ftimulus  be  with- 
drawn ; which  is,  that  the  fenforial  power  becomes  accumu- 
lated in  the  contraCtile  fibres,  owing  to  the  want  of  its  being 
perpetually  expended,  or  carried  away,  by  their  ufual  unre- 
rnitted  contractions.  And,  on  this  account,  thofe  mufcular 
fibres  become  afterwards  excitable  into  their  natural  aCtions 
by  a much  weaker  ftimulus  ; or  into  unnatural  violence  of  ac- 
tion, by  their  aecuftomed  ftimulus,  as  is  feen  in  the  hot  fits  of 
intermittent  fevers,  which  are  in  confequence  ot  the  previous 
cold  ones.  Thus  the  minute  veflfels  ot  the  (kin  are  conftant- 
ly  ftimulated  by  the  fluid  matter  of  heat;  it  the  quantity  ot  this 
ftimulus  of  heat  be  a while  diminifhed,  as  in  covering  the 
hands  with  fnow,  the  veflels  ceafe  to  adt,  as  appears  from  the 
palenels  of  the  fkin  ; if  this  cold  application  of  fnow  be  conti- 
nued but  a Abort  time,  the  fenforial  power,  which  had  habitu- 
ally been  fupplied  to  the  fibres,  becomes  now  accumulated  ::i 
them,  owing  to  the  want  of  its  being  expended  by  their  accul- 
tomed  contractions.  And  thence  a lei's  ftimulus  of  heat  will 
now  excite  them  into  violent  contractions. 


Sect.  XII.  2.  OF  STIMULUS  AND  EXERTION.  55 

If  the  quiefcence  of  fibres,  which  had  previoufly  been  fub- 
je<£t  to  perpetual  ftimulus,  coptinv.es  a longer  time,  or  their  ac- 
cuftomed  ftimulus  be  more  completely  withdrawn,  the  accu- 
mulation of  fenforial  power  becomes  ftill  greater,  as  in  thofe 
expofed  to  cold  and  hunger;  pain  is  produced,  and  the  organ 
gradually  dies  from  the  chemical  changes  which  take  place  in 
It;  or  it  is,  at  a great  di  fiance  of  time,  reflored  to  addion  by  fti- 
mulus  applied  with  great  caution,  in  fmail  quantity,  as  hap- 
pens to  feme  larger  animals,  and  to  many  iniedts,  which,  dur- 
ing the  winter  months,  lie  benumbed  with  cold,  and  are  laid  to 
fleep,  and  to  perfons  apparently  drowned,  or  apparently  frozen 
to  death.  Snails  have  been  faid  to  revive  by  throwing  them 
into  water,  after  having  been  many  years  fhut  up  in  the  cabi- 
nets of  the  curious ; and  eggs  and  feeds  in  general,  are  reflored 
to  life  after  many  months  of  torpor  by  the  ftimulus  of  warm 
water  and  moiflure. 

The  inflammation  of  fthirrous  tumours,  which  have  long 
exifted  in  a flate  of  inaction,  is  a procels  of  this  kind,  as  well 
as  the  fenfibility  acquired  by  inflamed  tendons  and  bones, 
which  had,  at  their  formation,  a fimilar  fenfibility,  which  had 
fo  long  lain  dormant  in  their  uninflamed  (late. 

3.  If,  after  long  quiefcence  from  defeCl  of  ftimulus,  the  fi- 
bres, which  had  previoufly  been  habituated  to  perpetual  fti- 
muls,  are  again  expofed  to  but  their  uiual  quantity  of  it,  as 
in  thofe  who  have  fuffered  the  extremes  of  cold  or  hunger,  a 
violent  exertion  of  the  affeCled  organ  commences,  owing,  as 
above  explained,  to  the  great  accumulation  of  fenforial  power. 
This  violent  exertion  not  only  diminifhes  the  accumulated  fpi- 
lit  of  animation,  but,  at  the  fame  time,  induces  pleafure  or 
pain  into  the  fyflem,  w'hich,  whether  it  be  fucceeded  by  in- 
flammation or  not,  becomes  an  additional  ftimulus,  and  adding 
along  with  the  former  one,  produces  ftill  greater  exertions,  and 
thus  reduces  the  fenforial  power,  in  the  contracting  fibres,  be- 
neath its  natural  quantity. 

When  the  fpirit  of  animation  is  thus  exhaufted  'by  ufelefs 
exertions,  the  organ  becomes  torpid,  or  unexcitable  into  aCticn, 
and  a fecond  fit  of  quiefcence  fucceeds  that  of  abundant  acti- 
vity. During  this  fecond  fit  of  quiefcence,  the  fenforial 
power  becomes  again  accumulated,  and  another  fit  of  exer- 
tion follows  in  train.  Thefe  viciffitudes  of  exertion  and  in- 
ertion  of  the  arterial  fyflem,  conftitute  the  paroxyfms  of  re- 
mittent fevers ; or  intermittent  ones,  when  there  is  an  interval 
of  the  natural  aCtion  of  the  arteries  between  the  exacerbations. 

In  thefe  paroxyfms  of  fevers,  which  confift  of  the  libration 
of  the  arterial  lyilem,  between  the  extremes  of  exertion  and 

quiefcence, 


S6  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  3. 

quiefcence,  either  the  fits  become  lefs  and  lefs  violent,  from 
the  contraftile  fibres  becoming  lefs  and  lefs  excitable  to  the  fti- 
mulus  by  habit,  that  is,  by  becoming  accuftomed  to  it,  as  ex- 
plained below,  XII.  3.  1.  or  the  whole  fenforial  power  be- 
comes exhaufled,  and  the  arteries  ceafe  to  beat,  and  the  patient 
dies  in  the  cold  part  of  the  paroxyfm.  Or,  fecOndly,  io  much 
pain  is  introduced  into  the  fyftem  by  the  violent  contractions 
of  the  fibres,  that  inflammation  arifes,  which  prevents  future 
cold  fits,  by  expending  a part  of  the  fenforial  power  in  the  ex- 
tenfion  of  old  veflcls  or  the  production  of  new  ones,  and  thus 
preventing  the  too  great  accumulation  or  exertion  of  ic  in  other 
parts  of  the  fyftem  ; or  which,  by  the  great  increase  eft  ftimu- 
■lus,  excites  into  great  action  the  whole  glandular  fyftem,  as 
well  as  the  arterial,  and  thence  a greater  quantity  of  fenforial 
power  is  produced  in  the  brain,  and  thus  its  exhauftion  in  any 
peculiar  part  of  the  fyftem,  ceafes  to  be  affefted. 

4.  Or,  thirdly,  in  confequence  of  the  painful  or  pleafurable 
fenfation  above  mentioned,  defire  and  averfion  are  introduced, 
and  inordinate  volition  fucceeds ; which,  by  its  own  exertions, 
expends  fo  much  of  the  fpirit  of  animation,  that  die  two  other 
fenforial  faculties,  or  irritation  and  fenfation,  aft  fo  much  fee- 
bler, that  the  paroxyfms  of  fever,  or  that  libration  between  the 
extremes  of  exertion  and  inaftivity  of  the  arterial  fyftem,  gra- 
dually fublides.  On  this  account  a temporary  infanity  is  a 
favourable  fign  in  fevers,  as  I have  had  fome  opportunities  o 1 
obferving. 

III.  Of  repeated  Stimulus. 

1.  When  a ftimulus  is  repeated  more  frequently  than  the 
expenditure  of  fenforial  power  can  be  renewed  in  the  afting 
organ,  the  efteft  of  the  ftimulus  becomes  gradually  dimiuilli- 
■ed.  Thus,  if  two  grains  of  opium  be  fvvallowed  bv  a perfon 
unufed  to  fo  ftrong  a ftimulus,  all  the  vafcular  fyftems  in  the 
body  aft  with  greater  energy  ; all  the  fecretions  and  the  abforp- 
tion  from  thofe  fecreted  fluids  are  in'ereafed  in  quantity  ; and 
pleafure  or  pain  are  introduced  into  the  fyftem,  which  adds  an 
additional  ftimulus  to  that  already  too  great.  After  iome 
hours  the  fenforial  power  becomes  di  mini  (bed  in  quantity,  ex- 
pended by  the  great  aftivity  of  the  fyftem  ; and  thence,  when 
the  ftimulus  of  the  opium  is  withdrawn,  the  fibres  will  not 
obey  their  ufual  degree  of  natural  ftimulus,  and  a confequent 
torpor  or  quiefcence  fucceeds,  as  is  experienced  by  drunkards, 
who,  on  the  day  after  a great  excels’ of  fpirituous  potation, 
feel  indigeftion,  head-ach,  and  general  debility. 

In  this  fit  of  torpor  or  quiefcence  of  a part  or  of  die  whole 

of 


Sect.  XII.  3.  OF  STIMULUS  AND  EXERTION.  57 

of  the  fyftem,  an  accumulation  of  the  fenlorial  power  in  the 
affedfed  hbres  is  formed,  and  occafions  a fecond  paroxvfm  of 
exertion,  by  the  application  only  of  the  natural  ftimulus ; and 
thus  a libration  of  the  fenlorial  exertion  between  one  excels 
and  the  other,  continues  for  two  or  three  days,  where  the  fti- 
mulus was  violent  in  degree ; and  for  weeks  in  feme  fevers, 
from  the  ftimulus  of  contagious  matter. 

But  if  a fecond  dofe  of  opium  be  exhibited  before  the  fibres 
have  regained  their  natural  quantity  of  lenforial  power,  its  ef- 
fect will  be  much  lei's  than  the  former,  becaufe  the  fpirit  of 
animation,  or  fenforial  power,  is  in  part  exhaufted  by  the  pre- 
vious excefs  of  exertion.  Hence  all  medicines,  repeated  too 
frequently,  gradually  lofe  their  effedt,  as  opium  and  wine. 
Many  things  of  difagreeable  tafte  at  firft,  ceafe  to  be  difagree- 
ble  by  frequent  repetition,  as  tobacco ; grief  and  pain  gradually 
diminilh,  and  at  length  ceafe  altogether and  hence  life  itfelf 
becomes  tolerable. 

Befides  the  temporary  diminution  of  the  fpirit  of  animation 
or  fenforial  power,  which  is  naturally  ftationary  or  refident  in 
every  living  fibre,  by  a fingle  exhibition  of  a powerful  ftimulus, 
the  contradlile  fibres  themfelves,  by  the  perpetual  application 
of  a new  quantity  of  ftimulus,  before  they  have  regained  their 
natural  quantity  of  fenforial  power,  appear  to  fuller  in  their 
capability  of  receiving  fo  much  as  the  natural  quantity  of  fen- 
forial power ; and  hence  a permanent  deficiency  of  fpirit  of  ani- 
mation takes  place,  however  long  the  ftimulus  may  have  been 
withdrawn.  On  this  caufe  depends  the  permanent  debility  of 
thofe  who  have  been  addidfed  to  intoxication,  the  general  weak- 
hefs  of  old  age,  and  the  natural  debility  or  irritability  of  thofe 
who  have  pale  fkins  and  large  pupils  of  their  eyes. 

There  is  a curious  phenomenon  belongs  to  this  place,  which 
has  always  appeared  difficult  of  folution ; and  that  is,  that  opium 
or  aloes  may  be  exhibited  in  fmall  doles  at  firft,  and  gradually 
increafed  to  very  large  ones,  without  producing  ftupor  or  diarr- 
hoea. In  this  cafe,  though  the  opium  and  aloes  are  given  in 
fuch  fmall  dofes  as  not  to  produce  intoxication  or  catharfis,  yet 
they  are  exhibited  in  quantities  fufficient,  in  fome  degree,  to 
exhauft  the  fenforial  power,  and  hence  a ftronger  and  a ftronger 
dofe  is  required;  otherwife  the  medicine  would  icon  ceafe  to 
adt  at  all. 

On  the  contrary,  if  the  opium  or  aloes  be  exhibited  in  a 
large  dofe  at  firft,  fo  as  to  produce  intoxication  or  diarrhcea, 
after  a few  repetitions  the  quantity  of  either  of  them  may  be 
diminifhed,  and  they  will  ftill  produce  this  effedt  For  the 
more  powerful  ftimulus  diffevers  the  pwgreffive  catenations  of 

animal 


58  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  3. 

animal  motions,  defcribed  in  Seel.  XVII.  and  introduces  a 
new  link  between  them;  whence  every  repetition  ftrengthens 
this  new  atTociation  or  catenation,  and  the  ftimulus  mav  be 
gradually  decreafed,  or  be  nearly  withdrawn,  and  yet  the  effect 
fhall  continue,  becaufe  the  fenforial  power  of  affociation  or 
catenation,  being  united  with  the  ftimulus,  increafes  in  energy 
with  every  1'epetition  of  the  catenated  circle;  and  it  is  bv  thele 
means  that  all  the  irritative  affociations  of  motions  are  origi- 
nally produced. 

2.  When  a ftimulus  is  repeated  at  fuch  diftant  intervals  of 
time,  that  the  natural  quantity  of  fenforial  power  becomes 
completely  reftored  in  the  acting  fibres,  it  wiil  act  with  the 
fame  energy  as  when  firft  applied.  Hence  tin  ft  who  have 
lately  accuftomed  themfelves  to  large  dofes  of  opium,  by  begin- 
ning with  fmall  ones,  and  gradually  increafmg  them,  and  re- 
peating them  frequently,  as  mentioned  in  the  preceding  para- 
graph, if  they  intermit  the  ufe  of  it  for  a few  days  only,  mu  ft 
begin  again  with  as  fmall  dofes  as  they  took  at  firft;  otherwife 
they  will  experience  the  inconveniences  of  intoxication. 

On  this  circumftance  depend  the  conftant  unfailing  effects 
of  the  various  kinds  of  ftimulus,  which  excite  into  action  all 
the  vafcular  fvftemsjn  the  body ; the  arterial,  venous,  ablorb- 
cnt,  and  glandular  veftels,  are  brought  into  perpetual,  unwea- 
ried action  by  the  fluids,  which  are  adapted  to  ftimulate  them; 
but  thefe  have  the  fenforial  power  of  affociation  added  to  that 
of  irritation,  and  even,  in  fome  degree,  that  of  fenfation,  and 
even  of  volition,  as  wiil  he  fpoken  of  in  their  places ; and  life 
itleif  is  thus  carried  on  by  the  production  of  fenforial  power 
being  equal  to  its  wafte  or  expenditure  in  the  perpetual  move- 
ment of  the  vafcular  organization. 

O m „ 

3.  When  a ftimulus  is  repeated  at  uniform  intervals  of  time, 
with  fuch  diftances  between  them  that  the  expenditure  of  fen- 
forial power  in  the  acting  fibres  becomes  completely  renewed, 
the  effect  is  produced  with  greater  facility  or  energy.  For 
the  fenforial  power  of  affociation  is  combined  with  the  fenfo- 
rial power  of  irritation;  or,  in  common  language,  the  acquired 
habit  affifts  the  power  of  die  ftimulus. 

This  circumftance  not  only  obtains  in  the  annual  and  diur- 
nal catenations  of  animal  motions,  explained  in  Sect.  XXXVI. 
but  in  every  lefs  circle  of  actions  or  ideas,  as  in  the  burdien  of 
a fong,  or  the  iterations  of  a dance,  and  conftitutes  the  plea- 
fure  we  receive  from  repetition  and  imitation,  as  treated  of  in 
Sect.  XXII.  2. 

4.  When  a ftimuluihas  been  many  times-  repeated  at  uni- 
form intervals,  fo  as  tPproduce  the  complete  action  of  the  or- 


Sect.  XII.  3.  OF  STIMULUS  AND  EXERTION,  59 

gan,  it  may  then  be  gradually  diminifhed,  or  totally  with- 
drawn, and  the  adtion  of  the  organ  will  continue ; for  the 
fenforial  power  of  affociation  becomes  united  with  that  of  ir-* 
ritation,  and  by  frequent  repetition  becomes  at  length  of  fuffi- 
cient  energy  to  carry  on  the  new  link  in  the  circle  of  adtions, 
without  the  irritation  which  at  firft  introduced  it, 

Hence,  when  the  bark  is  given  at  ftated  intervals  for  the  cure 
of  intermittent  fevers,  if  fixty  grains  of  it  be  given  every  three 
hours  for  the  twenty-four  hours  preceding  the  expected  parox- 
vfm,  fo  as  to  Simulate  the  defective  pan  of  the  fyftem  into 
adtion,  and  by  that  means  to  prevent  the  torpor  or  quiefcence 
of  the  fibres,  which  conftitutes  the  cold  fit ; much  le.s  than 
half  the  quantity,  given  before  the  time  at  which  another  pa- 
roxyfm  of  quiefcence  would  have  taken  place,  will  be  luffi- 
cient  to  prevent  it ; becaufe  now  the  fenforial  power,  termed 
affociation,  adts  in  a twofold  manner.  Find,  in  refpedl  to 
the  period  of  the  catenation  in  which  the  cold  fit  was  produced, 
which  is  now  diffevered  by  the  ftronger  ftimulus  of  the  firft 
dofes  of  the  bark;  and,  fecondly,  becaufe  each  dofe  of  bark 
being  repeated  at  periodical  times,  has  its  effedl  increafed  by 
the  fenforial  faculty  of  affociation  being  combined  with  that 
of  irritation. 

Now,  when  fixty  grains  of  Peruvian  bark  are  taken  twice 
a day,  fuppofe  at  ten  o’clock  and  at  fix,  for  a fortnight,  the  ir- 
ritation excited  by  this  additional  ftimulus  becomes  a part  of 
the  diurnal. circle  of  adfions,  and  will  at  length  carry  on  the 
increafed  action  of  the  fyftem  without  the  afliftance  of  the  fti- 
mulus of  the  bark.  On  this  theory  the  bitter  medicines,  cha- 
lybeates,  and  opiates  in  appropriated  dofes,  exhibited  for  a 
fortnight,  give  permanent  ftrength  to  pale,  feeble  children,  and 
other  weak  conftitutions. 

5.  When  a defect  of  ftimulus,  as  of  heat,  recufs  at  certain 
diurnal  intervals,  which  induces  fome  torpor,  or  quiefcence  of 
a part  of  the  fyftem,  the  diurnal  catenation  of  adtions  becomes 
difordered,  and  a new  affociation  with  this  link  of  torpid  ac- 
tion is  formed ; on  the  next  period  the  quantity  of  quiefcence 
will  be  increafed,  fuppofe  the  fame  defedt  of  ftimulus  to  recur ; 
becaufe  now  the  new  affociation  confpires  with  the  defective 
irritation  in  introducing  the  torpid  action  of  this  part  of  the 
diurnal  catenation.  In  this  manner  many  fever-fits  commence, 
where  the  patient  is  for  fome  days  indifpoled  at  certain  hours, 
before  the  cold  paroxyl'm  of  fever  is  completely  formed.  See 
Sedt.  XVII.  3.  3.  on  catenation  of  animal  motions. 

6.  If  a ftimulus,  which  at  firft  excited  the  affedted  organ 
into  fo  great  exertion  as  to  produce  feAjtion,  be  continued 

K for 


60  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  4. 

for  a certain  time,  it  will  ceafe  to  produce  fenfation  both  then 
anu  when  repeated,  though  the  irritative  motions  in  confe- 
quence of  it  may  continue  or  be  re-excited. 

Many  catenations  of  irritative  motions  were  at  firft  Suc- 
ceeded by  fenfation,  as  the  apparent  motions  of  objects  when 
we  walk"  paft  them,  and  probably  the  vital  motions  themfeives 
in  the  early  ftate  of  our  exiftence.  But  as  thofe  fenfations 
were  followed  by  no  movements  of  the  fyflem  in  confequence 
of  them,  they  gradually  ceafed  to  be  produced,  not  being  join- 
ed  to  any  fucceeding  link  of  catenation.  Hence  contagious 
matter,  which  has  for  feme  weeks  (Emulated  the  fyftem  into 
great  and  permanent  fenfation,  ceafes  afterwards  to  produce 
general  fenfation,  or  inflammation,  though  it  may  ftiii  induce 
topical  irritations.  See  Sett.  XXXIII.  2.  8.  XIX.  10. 

Our  abi’orbent  fyftem  then  feems  to  receive  thofe  contagious 
matters,  which  it  has  before  experienced,  in  the  fame  manner 
as  it  imbibes  common  moifture,  or  other  fluids ; that  is.  with- 
out being  thrown  into  fo  violent  adlion  as  to  produce  fenfa- 
tion ; the  confequence  of  which  is  an  increafe  of  daily  energy  or 
activity,  til!  inflammation  and  its  confequences  fucceed. 

7.  If  a ftimulus  excites  an  organ  into  fuch  violent  contrac- 
tions as  to  produce  fenfation,  tire  motions  of  which  organ  had 
not  ufually  produced  fenfation,  this  new  fenforial  power,  added 
to  the  irritation  occalioned  by  the  ftimuius,  increafes  the  acti- 
vity of  the  organ.  And  if  this  activity  be  catenated  with  the 
diurnal  circle  of  aCtions,  an  increaftng  inflammation  is  produc- 
ed, as  in  the  evening  paroxyfms  of  imali-pox,  and  other  fevers 
with  inflammation:  and  hence  fchirrous  tumours,  tendons,  and 
membranes,  and  probably  the  arteries  themielves,  become  in- 
flamed, when  they  are  ftrongly  ftimulated. 

IV.  Of  Stimulus  greater  than  natural. 

1.  A quantity  of  ftimulus  greater  than  natural,  producing 
an  increafed  exertion  of  fenforial  power,  whether  that  exertion 
be  in  the  mode  of  irritation,  fenfation,  volition,  or  affociation, 
dim: a: mas  the  general  quantity  of  it.  This  facl  is  obfervable 
in  the  pfogrefs  of  intoxication,  as  the  increafed  quantity  or 
energy  of  the  iri  ita live  motions,  owing  to  the  ftimulus  of  vi- 
nous ipifit,  introduces  much  pleafurable  fenfation  into  the  fyf- 
tem, and  much  exertion  of  mufcular  or  fenfual  motions  in  con- 
fequence of  this  increafed  fenfation , the  voluntary  motions, 
and  even  the  affociate  ones,  become  much  impaired  or  dimi- 
nilhed,  anu  delirium  and  {daggering  fucceed.  See  Sedl.  XXI. 
on  drunkennefs.  And  hence  the  great  proftration  of  the 
ftrengdr  of  the  locoaflfcve  ihufcles  in  fome  fevers,  is  owing  to 
* ' the 


Sect.  XII.  4-  OF  STIMULUS  AND  EXERTION.  61 

the  exhauftion  of  fenforial  power,  by  the  increafed  action  of 
the  arterial  fyflem. 

In  like  manner  a ftimulus  greater  than  natural,  applied  to  a 
part  of  the  fyftem,  increafes  the  exertion  of  tentorial  power  in 
that  part,  and  diminifhes  it  in  fome  other  part.  As  in  the 
commencement  of  fcarlet  fever,  it  is  ufual  to  iee  great  rednefs 
and  heat  on  the  laces  and  breafts  of  children,  while,  at  the  fame 
time,  their  feet  are  colder  than  natural ; partial  heats  are  obferv- 
able  in  other  fevers  with  debility,  and  are  generally  attended 
with  torpor,  or  quiefcence  of  fome  other  part  of  the  fyftem. 
But  thefe  partial  exertions  of  fenforial  power  are  fometimes 
attended  with  increafed  partial  exertions  in  other  parts  of  the 
fyftem,  which  fympathize  with  them,  as  the  flufhing  of  tire 
lace  after  a full  meal.  But  thefe,  therefore,  are  to  be  afcrib'ed 
to  fympathetic  affociations,  explained  in  Seel,  XXXV.  and  not 
to  general  exhauftion.  or  accumulation  of  leniorial  power. 

2.  A quantity  of  ftimulus  greater  than  natural,  producing 
an  increafed  exertion  of  fenforial  power  in  any  particular  or- 
gan, diminifhes  the  quantity  of  it  in  that  organ.  This  appears 
from  the  contradlions  of  animal  fibres  being  not  fo  eafily  excit- 
ed by  a left;  ftimulus,  after  the  organ  has  been  fubjecled  to  a 
greater.  Thus,  after.!  looking  at  any  luminous  objedt  of  a 
fmall  lize,  as  at  the  fetting  fun  for  a fhort  time,  fo  as  not  much 
to  fatigue  the  eye,  this  part  of  the  retina  becomes  lefs  fenftble 
to  fmaller  quantities  of  light:  hence,  when-  the  eyes  are  turned 
on  other  lefs  luminous  parts  Gf  the  Iky,  a dark  fpot  is  feen  re- 
lembling  the  fhape  of  the  fun,  or  other  luminous  object  which 
we  laft:  beheld.  'See  Sedt.  XL.  No.  2. 

Thus  we  are  fome  time  before  we  can  diftinguifti  objedts  in 
an  obfeure  room  after  coming  from  bright  day-light,  though 
the  iris  prefently  contradls  itlelfl  We  are  not  able  to  hear 
weak  founds  after  loud  ones.  And  the  ftomachs  of  thofe  who 
have  been  much  habituated  to  the  ftronger  ftimulus  of  ferment- 
ed or  fpirituous  liquors,  are  not  excited  into  due  adiion  by 
weaker  ones. 

3.  A quantity  of  ftimulus  fomething  greater  than  the  laft 
mentioned,  or  longer  continued,  induces  the  organ  into  fpaf- 
medic  adiion,  which  ceales  and  recurs  alternately.  Thus,  on 
looking  for  a time  on  the  fetting  fun,  fo  as  not  greatly  to  fatigue 
the  light,  a yellow  fpedfrum  is  feen  when  the  eyes  are  clofed 
and  covered,  which  continues  for  a time,  and  then  diiappears 
and  recurs  repeatedly  before  it  entirely  vaniflres.  See  Sedl- 
XL.  No.  5.  Thus  the  adiion  of  vomiting  ceafes  and  is  re- 
newed by  intervals,  although  the  err^^  drug  is  thrown  up 
with  tire  firft  etrort,.  A tenefmus  cc^Jfcucs  by  intervals  fome 

time 


62  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  4. 

time  after  the  exclufion  of  acrid  excrement;  and  the  pulfations  • 
of  the  heart  of  a viper  are  faid  to  continue  l'ome  time  after  it  ft 
cleared  from  its  blood. 

In  thefe  cafes,  the  violent  contradlions  of  the  fibres  produce 
pain,  according  to  law  4;  and  this  pain  conffcirutes  an  additional 
kind  or  quantity  of  excitement,  which  again  induces  the  fi- 
bres into  contraction  ; and  which  painful  excitement  is  again 
renewed,  and  again  induces  contractions  of  the  fibres  with  gra- 
dually diminifhing  effed:. 

4.  A quantity  of  ftimulus  greater  than  that  lad  mentioned, 
or  longer  continued,  induces  the  antagonift  mufcles  into  fpaf- 
xnodic  addon.  This  is  beautifully  illuftrated  by  the  ocular 
fpedra,  defcribed  in  Sed.  XL.  No.  6,  to  which  the  reader  is 
referred.  From  thefe  experiments  there  is  reafon  to  conclude, 
that  the  fatigued  part  of  the  retina  throws  itfelf  into  a contrary 
mode  of  adion,  like  ofeitation  or  pandiculation,  as  foon  as  the 
ftimulus,  which  has  fatigued  it;  is  withdrawn  ; but  that  it  ftill 
remains  liable  to  be  excited  into  adion  bv  anv  ether  colours 
except  the  colour  with  which  it  has  been  fatigued.  Thus  the 
yawning  and  ftretching  the  limbs  after  a continued  adiion  or 
attitude,  feems  occafioned  by  the  antagonift  mufcles  being  fti- 
mulated  by  their  extenfton  during  the  contractions  of  thofe  in 
adion,  or  in  the  fituation  in  which  that  adion  left  left  them. 

5.  A quantity  of  ftimulus  greater  than  the  laft,  or  longer 
continued,  induces  variety  of  convulfions  01  fixed  ipafms,  ei- 
ther of  the  aff'eded  organ,  or  of  the  moving  fibres  in  other  parts 

' of  the  bodv.  In  refped:  to  the  fpedra  in  the  eye,. this  is  well 
illuftrated  in  No.  7 and  8 of  Sect.  XL.  Epileptic  convul- 
fions,  as  the  emprofthotonos  and  opifthotonos,  with  the  cramp 
of  the  calf  of  the  leg,  locked  jaw,  and  other  cataleptic  fits,  ap- 
pear to  orignate  from  pain,  as  fome  of  thefe  patients  feream 
aloud  before  the  convulfion  takes  place ; which  ieems  at  firft 
to  be  an  effort  to  relieve  painful  fenfation,  and  afterwards  an 
effort  to  prevent  it. 

In  thefe  cafes  the  violent  contradions  of  the  fibres  produce 
fo  much  pain,  as  to  conftitute  a perpetual  excitement ; and  that 
in  fo  great  degree,  as  to  allow  but  fmall  intervals  of  relaxation 
of  the  contrading  fibres,  as  in  convulfions;  or  no  interval^at 
all,  as  in  fixed  fpafms.  ’ 

6.  A quantity  of  ftimulus  greater  than  the  laft,  or  longer 
continued,  produces  a paralyiis  of  the  organ.  In  many  caies 
this  paralyfis  is  only  a temporary  effed,  as  on  looking  long  cn 
a fmall  aera  of  bright  red  filk,  placed  cn  a fheet  of  white  pa- 
per on  the  floor  in  a ft^ig  light,  the  red  fill:  gradually  becomes 
paler,  and  at  length ^■p,'CY.r>  which  evinces  that  a part  of 

• the 


Sect. XII.  5.  OF  STIMULUS  AND  EXERTION.  63 

the  retina,  by  being  violently  excited,  becomes  for  a time  un- 
affected by  the  famulus  of  that  colour.  Thus,  cathartic  me- 
dicines, opiates,  poifons,  contagious  matter,  ceafe  to  influence 
our  fy idem,  after  it  has  been  habituated  to  the  ufe  of  them,  ex-, 
cept  by  the  exhibition  of  inereafed  quantities  ot  them ; our  fi- 
bres not  only  become  unaffected  by  famuli,  by  which  they  have 
previouflv  been  violently  irritated,  as  by  the  matter  of  the  finall- 
pox  or  meafles ; but  they  alio  become  unaffected  by  ienfation, 
where  the  violent  exertions,  which  difabled  them,  were  in 
coniequence  of  too  great  quantity  of  fenfation.  And,  laftly, 
the  fibres,  which  become  difobedient  to  volition,  are  probably 
difabled  by  their  too  violent  exertions,  in  confequence  of  too 
great  a quantity  of  volition. 

After  every  exertion  of  our  fibres,  a temporary  paralyfis 
fucceeds,  whence  intervals  of  all  mufcular  contractions,  as 
mentioned  in  No.  3 and  4 of  this  Section  : the  immediate  cauie 
of  thefemore  permanent  kinds  of  par aly fiscs  probably  owing,  in 
the  fame  manner,  to  the  too  great  exhauftion  of  the  fpirit  of 
animation  in  the  affected  part ; fo  that  a ftronger  ftimulus  is 
required,  or  one  of  a different  kind  from  that  which  occafion- 
ed  thofe'two  violent  contractions,  to  again  excite  the  affected 
organ  into  activity ; and  if  a ftronger  ftimulus  could  be  appli- 
ed, it  muff  again  induce  paralyfis. 

For  thefe  powerful  ftimuli  .excite  pain  at  the  fame  time  that 
they  produce  irritation ; and  this  pain  not  only  excites  fibrous 
motions  by  its  ftimulus,  but  it  alio  produces  volition;  and  thus 
all  thefe  ftimuli  acting  at  the  fame  time,  and  fometimes  with  ‘ 
the  addition  of  their  affociations,  produce  fo  great  exertion  as 
to  expend  the  whole  of  the  feniorial  power  in  the  affected 
fibres.  - -> 

V.  Of  Stimulus  lefs  than  natural. 

x.  A quantity  of  ftimulus  lefs  than  natural,  producing  a 
decreafed  exertion  of  fenforial  power,  occafions  an  accumula- 
tion of  ic.  This  circumftance  is  obfervable  in  the  haemipla- 
gia,  in  which  the  patients  are  perpetually  moving  the  muffles 
which  are  unaffected.  On  this  account  we  awake  with  greater 
vigour  after  deep,'  becaufe,  during  fo  many  hours,  the  great 
ufual  expenditure  of  fenforial  porter  in  the  performance  of  vo- 
luntary actions,  and  in  the  exertions  of  our  organs  ot  fenfe,  in 
coniequence  of  the  irritations  occafionedbv  external  objedts, 
had  been  fufpended,  and  a cenfequent  accumulation  had  taken 
place. 

In  like  manner  the  exertion  of  the  faaforial  power  lefs  than 
natural  in  one  pah  of  the  fyftem,  is  liatiJPo  produce  an  increafe 

of 


64  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  s. 

of  the  exertion  of  it  in  fome  other  part.  Thus,  bv  the  action 
of  vomiting,  in  which  the  natural  exertion  of  the  motions  of 
the  flomach  are  deftroyed  or  diminifhed,  an  increafed  ubforp- 
tion  of  the  pulmonary  and  cellular  lymphatics  is  produced,  as 
is  known  by  the  increafed  abforption  of  the  fluid  depofited  in 
them  in  dropfical  cafes.  But  thefe  partial  quiefcences  of  fen - 
forial  power,  are  alfo  fometimes  attended  with  other  partial 
quiefcences,- which  fympathize  with  them,  as  cold  and  pale  ex- 
tremities from  hunger.  Thefe,  therefore,  are  to  be  afcribed 
to  the  afTociations  of  fympathy.  explained  in  Seel.  XXXV. 
and  not  to  the  general  accumulation  of  fenforial  power. 

2.  A quantity  of  ftimulus  lefs  than  natural,  applied  to  fibres 
nrevioufty  accuftomed  to  perpetual  ftimulus,  is  fucceeacd  by 
accumulation  of  fenforial  power  in  the  affected  organ.  The 
truth  of  this  proportion  is  evinced,  becaufe  a ftimulus  lefs 
than  natural,  if  it  be  fomewhat  greater  than  that  above  men- 
tioned, will  excite  the  organ  fo  circumftanced  into  violent  ac- 
tivity. Thus,  or,  a trolly  day  with  wind,  the  face  of  a perfen 
expofed  to  the  wind  is  at  fir  ft  pale  and  fhrunk ; but  on  turning 
the  face  from  the  wind,  it  becomesToon  of  a glow  with  warmth 
and  fiufhing.  The  glow  of  the  ft; in  in  emerging  from  the 
cold-bath,  is  owing  to  the  fame  caufe. 

It  does  not  appear  that  an  accumulation  of  fenforial  power 
above  the  natural  quantity,  is  acquired  by  thofe  mufclcs  v/mch 
■are  not  fubjeft  to  perpetual  ftimulus,  as  the  locomotive  muf- 
-cles : thefe,  after  the  greateft  fatigue,  only  acquire  by  reft  their 
ufual  aptitude  to  motion ; whereas  the  vafeuiar  fyftem,  as  the 
heart  and  arteries,  after  a fhort  quiefcence,  are  thrown  into 
violent  adlion  by  their  natural  quantity  of  ftimulus. 

Neverthelefs,  by  this  accumulation  of  fenforial  power  during 
the  application  of  dccreafed  ftimulus,  and  by  the  exhau!  or. 
of  it  during  the  ariiion  of  increafed  ftimulus,  it  is  wifely  pro- 
vided, that  the  adlions  of  the  vafeuiar  mufcles  and  organs  of 
fenfe  are  not  much  deranged  by  fmall  variations  of  ftimulus; 
as  the  quantity  of  fenforial  power  becomes,  in  fome  meaiure, 
inverfely  as  the  quantity  of  ftimulus. 

3.  A quantity  of  ftimulus  lefs  than  that  mentioned  above, 
and  continued  for  fome  time,  induces  pain  in  the  affetfted  or- 
gan ; as  the  pain  of  cold  in  the  hands,  when  they  are  immerfed 
in  fnow,  is  owing  to  a deficiency  of  the  ftimulation  of  heat. 
Hunger  is  a pain  from  the  deficiency  of  the  ftimulation  of  food. 
Pain  in  the  back  at  the  commencement  of  ague-firs,  and  the 
Iiead-achs  which  attend  feeble  people,  are  pains  from  defect 
of  ftimulus,  and  araJieiice'  relieved  by  opium,  efientiai  oils, 
and  lpirit  of  wine, 


As 


SfcT.XII.  5.  OF  STIMULUS  AND  EXERTION.  65 

As  the  pains  which  originate  from  defedt  of  ftimulus  only 
occur  in  thoie  parts  of  the  fyftem  which  have  been  previouny 
iubjedted  to  perpetual  ftimulus ; and  as  an  accumulation  of 
feniorial  power  is  produced  in  the  quiefcent  organ  along  with 
the  pain,  as  in  cold  or  hunger,  there  is  reafon  to  believe,  that 
the  pain  is  owing  to  the  accumulation  of  fenforial  power. 
For,  in  the  locomotive  lmifcles,'  in  the  retina  of  the  eye,  and 
other  organs  of  fenfes,  no  pain  occurs  from  the  abfence  of  fti- 
mulus,  nor  any  great  accumulation  of  fenforial  power  beyond 
their  natural  quantity,  ftnce  thele  organs  have  not  been  ufed  to 
a perpetual  fupply  of  it.  There  is,  indeed,  a greater  accurnu - 
lation  occurs  in  the  organ  of  vifton  after  its  quiefcence,  becauie 
it  is  fubjedt  to  more  conftant  ftimulus. 

4.  A certain  quantity  of  ftimulus  lefs  than  natural,  induces 
the  moving  organ  into  feebler  and  more  frequent  contractions, 
as  mentioned  in  No.  I.  4.  of  this  Sedtion.  For' each  contrac- 
tion moving  through  a lefs  fpace,  or  with  lefs  force,  that  is, 
with  lefs  expenditure  of  the  fpirit  of  animation,  is  fooner  relax- 
ed, and  the  ipirit  of  animation,  derived  at  each  interval  into  the 
adting  fibres,  being  lefs,  thefe intervals  likewife  become  fhorter. 
Hence  the  tremours  of  the  hands  of  people  accuftomed  to 
vinous  fpirit,  till  they  take  their  ufual  ftimulus ; hence  the 
quick  pulfe  in  fevers  attended  with  debility,  which  is  greater 
than  in  fevers  attended  with  firength ; in  the  latter,  the  pulfe 
feldom  beats  above  120  times  in  a minute,  in  the  former  it  fre- 
quently exceeds  140. 

It  mull;  be  obferved,  that  in  this  and  the  two  following  arti- 
cles, the  decreafed  adiion  of  the  fyftem  is  probably  more  fre- 
quently occafioned  by  deficiency  in  the  quantity  of  fenforial 
power,  than  in  the  quantity  of  ftimulus.  Thus  thofe  feeble 
confti  utions  which  have  large  pupils  of  their  eyes,  and  all  who 
labour  under  nervous  fevers,  feem  to  owe  their  want  of  natural 
quantity  of  adiivity  in  the  fyftem,  to  the  deficiency  of  fenforial 
power ; fince,  as  far  as  can  be  feen,  they  frequently  poflefs 
the  natural  quantity  of  ftimulus. 

5.  A certain  quantity  of  ftimulus,  lefs  than  that  above  men- 
tioned, inverts  the  order  of  fucceffive  fibrous  contractions ; as 
in  vomiting,  the  vermicular  motions  of  the  ftomach  and  duo- 
denum are  inverted,  and  their  contents  ejedted ; which  is  pro- 
bably owing  to  the  exhauftion  of  the  fpirit  of  animation  in  the 
adling  mufeies,  by  a previous  exceffive  ftimulus,  as  by  the  root 
of  ipecacuanha,  and  the  confequent  defedt:  of  fenfoiial  power. 
The  fame  retrogade  motions  affect  the  whole  inteftinal  canal 
in  ileus ; and  the  ceiophagus,  in  globus  hyftericus.  See  this 
farther  explained  in  Sedt.  XXIX,  No.lflfe,  on  Retrogade  Mo- 
tions. 

I muft 


66  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  6. 

I muft:  ofcferve,  alio,  that  fcmethirig  fimilar  happens  in  the 
produdtionof  our  ideas,  oi  fenfual  motions,  when  they  are  too 
weakly  excited : when  any  one  is  thinking  intenfely  about  one 
thing,  and  carelefsly  converting  about- another,  he  is  liable  to 
ufe  the  word  of  a contrary  meaning  to  that  which  he  defined., 
as  cold  weather  for  hot  weather,  fummer  for  winter. 

6.  A certain  quantity  of  flimulus,  lei's  than  that  above  men 
tioned,  is  fucceeded  byparalyfis,  firft  of  the  voluntary  and  fen- 
fitive  motions,  and  afterwards  of  thcfe  of  irritation  and  of 
aflociation,  which  conftitute  death. 

VI.  Cure  of  iricreafcd  exertion. 

i.  The  cure  which  nature  has  provided  for  the  increased 
exertion  of  any  part  of  the  fyftem,  coniifts  in  the  confequent 
expenditure  of  the  feniorial  power.  But  as  a greater  torpor 
follows  this  exhauftion  ot  fenforial  power,  as  explained  in  the 
next  paragraph,  and  a greater  exertion  fucceeds  this  torpor, 
the  conftitution  frequently  links  under  thefe  increahng  libra- 
tions,  between  exertion  and  quiefcence,  till  at  length  complete 
qmefcence,  that  is,  death,  doles  the  fcene. 

For,  during  the  great  exertion  of  the  fyftem  in  the  hot  fit  of 
fever,  an  increafe  of  ftimulus  is  produced  from  the  greater  mo- 
mentum of  the  blood,  the  greater  diftention  of  the  heart  and 
arteries,  and  die  increafed  produdiion  of  heat,  by  the  violent 
adtions  of  the  fyftem,  occaiioned  by  this  augmentation  of  fti- 
mulus ; the  fenforial  power  becomes  diminilhed  in  a few  hours 
much  beneath  its  natural  quantity,  the  veflels  at  length  ceui'e 
to  obey  even  thefe  great  degrees  of  ftimulus,  as  fhewn  :n  Sech 
XL.  g.  l . and  a torpor  of  the  whole  or  of  a part  of  the  fyftem 
enfues. 

Now,  as  this  fecond  cold  fit  commences  with  a greater  de- 
ficiency of  fenforial  power,  it  is  alfo  attended  wi  a greater 
deficiency  of  ftimulus  than  in  the  preceding  cold  fit , that  is, 
wdth  lefs  momentum  of  blood,  lefs  diftention  of  the  heart.  On 
this  account  the  fecond  cold  fit  becomes  more  violent  and  ot 
longer  duration  than  the  firft  ; and  as  a greater  accumulation 
of  fenforial  power  muft  be  produced  before  the  fyftem  or  vef- 
fels  will  again  obey  the  diminilhed  ftimulus,  it  follows,  dial 
the  fecond  not  fit  of  fever  will  be  more  violent  than  the  former 
one  : and  that  unlefs  fome  other  caufes  counteract  either  the 
violent  exertions  in  the  hot  fit,  or  the  great  torpor  in  the  cold 
fit,  life  will  at  length  be  extinguifhed,  by  the  expenditure  of  die 
whole  of  the  fenforial  power.  And  from  hence  it  appears, 
that  the  true  means  qf^uring  fevers  muft  be  iuch  as  decrease 
the  ahhon  of  the  fyft®  in  the  hot  fit,  and  increafe  it  in  the 

cold 


Ssct.  XII.  7.  OF  STIMULUS  AND  EXERTION.  67 

cold  fit;  that  is,  fuch  as  prevent  the  too  great  diminution  of 
fenforial  power  in  the  hot  fit,  and  the  too  great  accumulation 
of  it  in  the  cold  one. 

2.  Where  the  exertion  of  the  fenforial  powers  is  much  in- 
creafed,  as  in  the  hot  fits  of  fever  or  inflammation,  the  follow- 
ing are  the  ufual  means  of  relieving  it.  Decreafe  the  irrita- 
tions by  blood-letting,  and  other  evacuations ; by  cold  water 
taken  into  the  ftomach,  or  injedted  as  enema,  or  ufed  external- 
ly ; by  cold  air  breathed  into  the  lungs,  and  diffufed  over  the 
fkin ; with  food  of  lefs  ftimulus  than  the  patient  has  been  ac- 
cuftomed  to. 

3.  As  a cold  fir,  or  paroxyfm  of  inactivity  of  fome  parts 
of  the  fyftem,  generally  precedes  the  hot  fit,  or  paroxyfm  of 
exertion,  by  which  the  fenforial  power  becomes  accumulated  ; 
this  cold  paroxyfm  fhould  be  prevented  by  ftimulant  medicines 
and  diet,  as  wine,  opium,  bark,  warmth,  cheerfulnefs,  anger, 
furprife. 

4.  Excite  into  greater  adtion  fome  other  part  of  the  fyf- 
tem, by  which  means  the  fpirit  of  animation  may  be  in  part 
expended,  and  thence  the  inordinate  adb'ons  of  the  difeafed 
part  may  be  leffened.  Hence,  when  a part  of  the  fkin  adls 
violently,  as  of  the  face  in  the  eruption  of  the  finall-pox,  if 
the  feet  be  cold  they  fhould  be  covered.  Hence  the  ufe  of  a 
blifter  applied  near  a topical  inflammation.  Hence  opium 
and  warm  bada  relieve  pains  both  from  excels  and  defedt  of 
ftimulus. 

5.  Firffc  increafe  the  general  ftimulation  above  its  natural 
quantity,  which  may  in  fome  degree  exhauft  the  fpirit  of  ani- 
mation; and  then  decreafe  the  ftimulation  beneath  its  natural 
quantity.  Hence,  after  fudorific  medicines  and  warm  air,  the 
application  of  refrigerants  may  have  greater  effect,  if  they 
could  be  adminiflered  without  danger  of  producing  too  great 
torpor  of  fome  part  of  the  fyftem ; as  frequently  happens  to 
people  in  health  from  coming  out  of  a warm  room  into  the 
cold  air,  by  which  a topical  inflammation,  in  confequence  of 
torpor  of  the  mucous  membrane  of  the  noftril,  is  produced, 
and  is  termed  a cold  in  the  head. 

VII.  Cure  of  decreafed  Exertion. 

1.  Where  the  exertion  of  the  fenforial  powers  is  much 
decreafed,  as  in  the  cold  fits  of  fever,  a gradual  accumulation 
of  the  fpirit  of  animation  takes  place;  as  occurs  in  all  cafes 
where  inactivity  or  torpor  of  a part  of  the  fyftem  exifts ; 
this  accumulation  of  fenforial  power  increafes,  till  ftimuli  lefs 
than  natural  are  fufficient  to  throw  it*urto  action,  then  the 

L cold 


68  OF  STIMULUS  AND  EXERTION.  Sect.  XII.  7. 

cold  fit  ceafes ; and,  from  the  action  of  the  natural  .ftimuli,  a 
hot  one  fucceeds  with  incieafed  activity  of  the  whole  fyftem. 

So,  in  fainting  fits,  or  fyneope,  there  is  a temporary  deficien- 
cy of  fenforial  exertions,  and  a confequent  quiefcence  of  a 
great  part  of  the  fyftem.  This  quiefcence  continues,  till  the 
fenforial  power  becomes  again  accumulated  in  the  torpid  or- 
gans ; and  then  the  ufual  diurnal  ftimuli  excite  the  revivefcent 
parts  again  into  action;  but  as  this  kind  of  quiefcence  conti- 
nues hut  a (hort  time  compared  to  the  cold  paroxyfm  of  an 
ague,  and  lefs  affefts  the  circulatory  fyftem,  a lefs  fuperabun- 
dency  of  exertion  fucceeds  in  the  organs  previoufty  torpid,  and 
a lefs  excefs  of  arterial  activity.  See  Se6t.  XXXIV.  1.  6. 

2.  In  the  difeales  occafioned  by  a defedt  of  fenforial  exer- 
tion, as  in  cold  fits  of  ague,  hyfteric  complaint,  and  nervous 
fever,  the  following  means  are  thole  commonly  ufed.  1.  In- 
creafe  the  ftimulation  above  its  natural  quantity  forfome  weeks, 
till  a new  habit  of  more  energetic  contraction  of  the  fibres  is 
eftablifhed.  This  is  to  be  done  by  wine,  opium,  bar  k,  fteel, 
given  at  exadt  periods,  and  in  appropriate  quantities  lor  j:' 
thefe  medicines  be  given  in  inch  quantity  as  to  induce  the  leaft 
degree  of  intoxication,  a debility  fucceeds  from  the  ufe!  efs  ex- 
hauftion  of  fpirit  of  animation,  in  eonfequence  of  too  grear 
exertion  of  the  mufcles,  or  organs  of  fenfe.  To  thefe  irrita- 
tive ftimuli  fhould  be  added  the  fenlitive  ones  of  cheerful  ide 
hope,  attention. 

3.  Change  the  kind  of  ftimulus.  The  habits  acquired  bv 
the  conftitution  depend  on  fuch  nice  circumftanees,  that  when 
one  kind  of  ftimulus  ceafes  to  excite  the  fenforial  power  inm 
tire  quantity  of  exertion  neceflary  to  health,  it  is  often  iuffici- 
ent  to  change  the  ftimulus  for  another  apparently  fimiiar  in 
quantity  and  quality.  Thus,  when  wine  ceafes  to  ftimulatu 
the  conftitution,  opium,  in  appropriate  doles,  i'upplies  the  de- 
fedt;  and  the  contrary.  This  is  all'o  obferved  in  the  eftedl- 
of  cathartic  medicines ; when  one  lofes  its  power,  another,  ap- 
parently lefs  efficacious,  will  fuccc-ed.  Hence  a change  of 
diet,  drink,  and  ftimulating  medicines,  is  often  advantageous  in 
difeafes  of  debility. 

4.  Stimulate  the  organs,  whofe  motions  are  aftociated  with 
the  torpid  parts  of  the  fyftem.  The  adtions  of  die  minute  vel- 
fels  of  the  various  parts  of  the  external  fkin,  are  not  onh  ;i (lo- 
ci a ted  with  each  other,  but  are  ftronglv  aftociated  with  thole 
of  fome  ot  the  internal  membranes,  and  particularly  or  the 
ftomach'.  Hence,  when  the  exertion  ol  the  ftomath  is  lets 
than  natural,  and  indigeftion  and  heait-burn  fucceed,  nothing 
fo  certainly  removetyffiefe  fvmptoivn.  as  the  ftimulus  ot  a b! 


Sect.  XII.7.  OF  STIMULUS  AND  EXERTION.  69 

ter  on  the  back.  The  coldnefs  of  the  extremities,  as  of  the 
nofe,  ears,  or  lingers,  are  hence  the  bell  indication  for  the  fuc- 
cefsful  application  of  bidders'. 

r.  Decreafe  the  ftimulus  for  a time.  By  leflening  tb.e  quan- 
tity of  heat  for  2 minute  or  two,  by  going  into  the  cold  bath, 
a great  accumulation  of  fenforial  power  is  produced;  for,  not 
only  the  minute  veffels  of  the  whole  external  fkin,  for  a time 
become  inadiive,  as  appears  by  their  palenefs,  but  the  minute 
veffels  of  the  lungs  lofe  much  of  their  adhVity  alfo,  by  concert 
with  thofe  of  the  fkin,  as  appears  from  the  difficulty  of  breath- 
ing at  ffrft  going  into  cold  water.  On  emerging  from  the  bath, 
the  fenforial  power  is  thrown  into  great  exertion  by  the  ftimu- 
lus  of  tire  common  degree  of  the  warmth  of  the  atmol'phere, 
and  a great  production  of  animal  heat  is  the  confequence. 
The  longer  a perfon  continues  in  the  cold  bath,  the  greater 
muff  be  the  prefent  inertion  of  a great  part  of  the  fyftem,  and 
so  confequence,  a greater  accumulation  of  fenforial  power. 
Whence  M.  Pome  recommends  lome  melancholy  patients  to 
be  kept  from  two  to  fix  hours  in  fpring-water,  and  m baths 
jftill  colder. 

-6.  Decreafe  the  ftimulus  for  a time  below  the  natural,  and 
then  increafe  it  above  natural.  The  effedf  of  this  procefs, 
improperly  ufed,  is  feen  in  giving  much  food,  or  applying 
much  warmth,  to  thofe  who  have  been  previoufly  expofed  to 
great  hunger,  or  to  great  cold.  The  accumulated  fenforial 
power  is  thrown  into  fo  violent  exertion,  that  inflammations 
and  mortifications  fupervene,  and  death  clofes  the  cataftrophe. 
In  many  difeafes  this  method  is  the  moll  fuccefsful ; hence  the 
hark  in  agues  produces  more  certain  effedl  alter  the  previous 
exhibition  of  emetics.  In  difeafes  attended  with  violent  pain, 
opium  lias  double  the  effecSt,  if  venefedtlon  and  a cathartic  have 
been  previoufly  ufcJ.  On  this  feems  to  have  been  founded 
the  fuccefsful  practice  of  Sydenham,  who  ufed  venefcdlion  and 
a cathartic  in  choloriffs,  before  the  exhibition  of  the  bark,  fteel, 
and  opiates. 

7.  Prevent  any  unneceflary  expenditure  of  fenforial  power 
Hence,  in  levers  with  debility,  a decumbent  poflure  is  prefer- 
red, with  filenee,  little  light,  and  fuch  a quantity  of  heat  as  may 
prevent  any  chill  lenfation,  or  any  coldnefs  ot  the  extremities. 
The  pulfe  of  patients  in  fevers  with  debility,  increases  in  fre- 
quency above  ten  pulfations  in  a minute  011  their  riling  out  of 
bed.  For  the  expenditure  of  fenforial  power  to  prelerve  an 
credl  pofture  of  the  body,  adds  to  the  general  deficiency  of  it, 
and  thus  affefts  the  circulation. 

S.  The  longer  in  time,  and  the  greater  in  degree,  the  quie- 

l lcence 


jo  OF  STIMULUS  AND  EXERTION.  Sect.  XII.-. 

lienee  or  inertion  of  an  organ  has  been,  fo  that  it  ftill  retains 
life  or  excitability,  the  lefs  ftimulus  fliould  at  firft  be  applied  to 
it.  The  quantity  of  {Emulation  is  a matter  of  great  nicetv  to 
determine,  where  the  torpor  or  quiefcence  of  the  fibres  has 
been  experienced  in  a great  degree,  or  for  a conliderable  time, 
as  in  cold  fits  of  the  ague,  in  continued  fevers  with  great  debi 
lity,  or  in  people  famifhed  at  lea,  or  peri  filing  with  cold.  In 
the  two  laft  cafes,  very  minute  quantities  of  food  fiiould  be  firft 
{applied,  and  very  few  additional  degrees  of  heat.  In  die  two 
former  cafes,  but  little  ftimulus  ot  wine  or  medicine,  above 
what  they  had  been  lately  accuftomed  to,  fliould  be  exhibited, 
and  this  at  frequent  and  ftated  intervals,  fo  that  the  effect  ot 
one  quantity  may  be  obferved  before  the  exhibition  of  anodier. 

It  thefe  circa mftances  are  not  attended  to,  as  the  fenforial 
power  ^becomes  accumulated  in  the  quiefeent  fibres,  an  inor- 
dinate exertion  takes  place,  by  the  increafe  of  ftimulus  adding 
on  the  accumulated  quantity  of  fenforial  power,  and  either  the 
paralyfis,  or  death  of  the  contradtile  fibres  enfues,  from  die  to- 
tal expenditure  of  the  fenforial  purs  er  in  the  affected  organ, 
owing  to  this  increafe  of  exertion,  like  the  debility  after  intox- 
ication. Or,  fecondly,  the  violent  exertions  above  mentioned, 
produce  painful  fenfation,  which  becomes  a new  ftimulus,  and 
by  thus  producing  inflammation,  and  increafing  the  adtivitv  of 
the  fibres  already  too  great,  fooncr  exhaufts  the  whole  ot  the 
fenforial  power  in  die  acting  organ,  and  mortification  ; diat  is, 
the  death  of  the  part,  fupervenes. 

Hence  there  have  been  many  inftances  of  people,  whofe 
limbs  have  been  long  benumbed  bv  expofure  to  cold,  who  have 
loft  them  by  mortification,  on  their  being  too  liu'tily  brought 
to  the  fire ; and  of  others,  who  were  nearly  famished  at  fea,  who 
have  died  foon  after  having  taken  not  more  than  an  ufual  meal 
of  food.  I have  iieard  of  two  well  attefted  inftances  of  pa- 
tients, in  the  cold  fit  of  ague,  who  have  died  horn  the  exltibi- 
tion  of  gin  and  vinegar,  by  die  inflammation  which  enfued. 
And  in  many  fevers  attended  with  debility,  the  unlimited  ufe  of 
wine,  and  the  wanton  application  ot  blifters,  I believe,  have  de- 
ftroyed  numbers,  by  the  debility  confequent  to  too  great  {Emu- 
lation ; that  is,  by  the  exhauftion  of  the  fenforial  power  by  its 
inordinate  exertion. 

Wherever  the  lea  ft  degree  of  intoxication  cxifts,  a propor- 
tional debility  is  the  confequence ; but  there  is  a golden  rule,  bv 
which  the  neceffary  and  ufeful  quantity  of  ftimulus,  in  fevers 
with  debility,  may  be  afeertained.  When  wine  or  beer  are 
exhibited,  either  alone,  or  diluted  with  water,  it  the  piffle  be- 
comes flower,  the  ftimulus  is  of  a .proper  quantity,  and  lliould 


Sect.  XIII.  i.  OF  VEGETABLE  ANIMATION.  71  . 

be  repeated  every  two  or  three  hours,  or  when  the  pulfe  again 
becomes  quicker. 

In  the  chronical  debility,  brought  on  by  drinking  fpiiituous 
or  fermented  hquors,  there  is  another  golden  rule,  by  which  I 
have  fi’ccefsfully  directed  the  quantity  of  fpirit  which  they  may 
lately  ieffen,  for  there  is  no  other  means  by  which  they  can  re- 
cover their  health.  It  fhould  be  prernifed,  that,  where  the  power 
ofdigeftion  in  thefe  patients  is  totally  deftroyed,  there  is  not 
much  rcalon  to  expedt  a return  to  healthful  vigour. 

I nave  diredted  feveral  of  thefe  patients  to  omit  one  fourth 
part  of  the  quantity  of  vinous  fpirits  they -have  been  lately  ac- 
cuflomed  to  ; and  if  in  a fortnight  their  appetite  increafes,  they 
are  advifed  to  omit  another  fourth  part ; but  it  they  perceive 
that  them  digeftion  becomes  impaired  ter  the  want  cl  this  quan- 
tity of  fpirituous  potation,  they  are  advifed  to  continue  as  they 
are,  and  rather  bear  the  ills  they  have,  than  ritk  the  encounter 
of  greater.  At  the  fame  time,  fiefh-meat,  with  or  without  fpice, 
is  recommended,  with  Peruvian  bark,  and  Heel,  in  frr.all  quan- 
tities, between  their  meals,  and  half  a grain  of  opium,  or  a 
grain,  with  live  or  eight  grains  of  rhubarb  at  night. 


SECT.  XIII. 

OF  VEGETABLE  ANIMATION. 

I.  1.  Vegetables  are  irritable , mimofa,  dioneea  mufcipula. 
Vegetable  fecretions.  2.  Vegetable  buds  are  inferior  ani- 
mals,1 arc  liable  to  greater  or  lefs  irritability.  II.  Sta- 
mens and  pijtils  of  plants  Jheiu  marks  of fenjibihty.  III. 
Vegetables  pojfefs  Jome  degree  of  volition.  IV.  Motions 
of  plants  are'aJJb'ciated  like  thojc  of  animals.  V.  1.  Ve- 
getable fr allure  like  that  of  animals,  their  anthers  and 
fiigmas  arc  living  creatures.  Male-flowers  of  Vallijne- 
ria.  2.  Whether  vegetables  pojfefs  ideas  ? They  have 
organs  of  fenfe,  as  of  touch  and  Jmell,  and  ideas  of  exter- 
nal thin"  s. 

o 

I.  1.  TKE  fibres  of  the  vegetable  world,  as  well  as  thole 
of  the  animal,  are  excitable  into  a variety  ot  motion  by  the  ir- 
ritations of  external  obj eels.  This  appears  particularly  in  the 
mimoia  or  fenfitive  plant,  whofeleay.es  contrail  on  the  fiighteft 
injury:  the  diontea  mufcipula,  which  was  lately  brought  ever 
from  the  marines  of  America,  prefents  us  with  another  curi- 
ous milance.  ct  vegetable  irritability;  its  leaves  are  armed  with 

fpincs 


72  OF  VEGETABLE  ANIMATION.  Sect.  XIII.  r. 


fpinc-s  on  their  upper  edge,  and  are  fpread  on  the  ground  around 
their  Item;  when  an  infecft  creeps  on  any  of  the.n  in  its  paf- 
fage  to  the  flower  or  feed,  the  leaf  flruts  upli'.e  a flee',  rat-trap, 
and  deflroys  its  enemy.  See  Botanic  Garden,  Parr  JI.  note 
on  Siiene. 

The  various  Accretions  of  vegetables,  as  ,of  odours,  fruit, 
gum,  refin,  wax,  honey,  feem  brought  about  in  tire  faux  man- 
ner as  in  the  glands  of  animals : the  tafteiefs  moifiure  of  the 
earth  is  converted  by  the  hop-plant,  into  a bitter  juice  • as  by 
the  caterpillar  in  the  nut-flheil,  the  fweet  kernel  is  converted 
into  a bitter  powder.  While  the  powder  of  ablorption  in  the 
roots  and  barks  of  vegetables,  is  excited  into  adlion  bv  the  flu- 
ids applied  to  their  mouths,  like  the  lacleals  and  lympatics  of 
animals. 

2.  The  individuals  of  the  vegetable  world  may  be  conlidered 
as  inferior  or  lefs  perfedf  animals  ; a tree  is  a congeries  of  many 
living  buds,  and  in  this  refpedf  refembles  the  branches  of  coral- 
line, which  are  a congeries  of  a multitude  of  animals.  Each 
of  thefe  buds  of  a tree  Iras  its  proper  leaves  or  petals  for  lungs, 
produces  its  viviparous  or  its  oviparous  offspring  in  buds  or 
feeds;  has  its  own  roots,  which,  extending  down  tire  Hem  of 
the  tree,  are  interwoven  with  the  roots  of  the  other  buds,  and 
form  the  bark,  which  is  the  only  living  part  of  the  Item,  is 
annually  renewed,  and  is  lnperinduced  upon  the  former  baill, 
which  then  dies,  and,  with  its  ftagnated  juices  graduallv  har- 
dening into  -wood,  forms  the  concentric  circles  which  we  fey 
in  blocks  of  timber. 

The  following  circumftances  evince  the  individuality  of  the 
buds  of  trees.  Find,  there  are  many  trees  whole  whole  internal 
wood  is  perifhed,  and  j et  tire  branches  are  vegete  and  healthy. 
Secondly,  the  fibres  of  the  barks  of  trees  are  chiefly  longitudi- 
nal, refenrbiing  roots,  as  is  beautifulljr  ieen  in  thofe  prepared 
bat  ks  that  were  lately  brought  from  Otaheita.  Thirdly,  in  ho- 
rizontal wounds  of  tire  bark  of  trees,  the  fibres  of  the  upper 
lip  are  always  elongated  downwards  like  roots,  but  thole  of  the 
lower  lip  do  not  approach  to  meet  them.  Fourthly,  if  you 
wrap  wet  nrofs  round  any  joint  of  a vine,  or  cover  it  with  moift 
earth,  roots  will  flroot  out  from  it.  Fifthly,  by  the  inoculation 
or  engrafting  of  trees,  many  fruits  are  produced  from  one  ftem. 
Sixthly,  a new  tree  is  produced  from  a branch  plucked  from  an 
old  one,  and  let  in  the  ground.  Whence  it  appears,  that  the 
buds  of  deciduous  trees  are  l'o  many  annual  plants;  that  the 
bark  i?  a contexture  of  the  roots  of  each  individual  bud;  and 
that  tiie  internal  wood  is  of  no  other  ufc  but  to  l'upport  them 
in  the  air;  and  that  thus  they  refemble  the  animal  world  in  their 
individuality. 


The 


h ^ 
/•> 


Sect.  XIII.  4.  OF  VEGETAELE  ANIMATION. 

The  irritability  of  plants,  like  that  oi  animals,  appears  li- 
able to  be  increafed  or  decreased  by  habit;  tor  thole  trees  or 
throbs,  which  are  brought  from  a colder  climate  to  awarmei, 
put  on  their  leaves  and  blofloms  a fortnight  fooner  than  the 
indigenous  ones. 

Profeffor  Kalin,  in  his  travels  in  New- York,  obferves,  that 
the  apple-trees  brought  from  England,  bloflorm  a fortnight 
fooner  than  native  ones.  In  cur  country,  the  flmibs  that  are 
brought  a decree  or  uvo  from  the  north,  are  obierved  to  flou- 
i iih  better  titan  thofe  which  come  from  tite  fouth.  The  Sibe- 
rian barley  and  cabbage  are  faid  to  grow  larger  in  this  climate,, 
than  the  fimiiar  more  ibuthern  vegetables.  And  our  hoards  of 
roots,  as  of  potatoes  and  onions,  germinate  with  lefs  heat  in 
j'pnng,  after  they  have  been  accuftomed  to  the  winter’s  cold, 
than  in  autumn,  after  the  fummer’s  heat. 

11  The  ftamens  and  piftils  of  flowers  fhew  evident  marks 
of  feniibiiity,  not  only  from  many  of  the  ftamens  and  force 
piftils  approaching  to  each  other  at  thefeafon  cl  impregnation, 
but  from  many  of  them  clofing  their  petals  and  calyxes  during 
the  bold  parts  of  the  day.  For  this  cannot  be  aferibed  to  irri- 
tation, becaufe  cold  means  a deleft  of  the  Hamulus  of  heat : 
but,  as.  the  want  of  accuftomed  ftimuli  produces  pain,  as  in 
coldnefs,  hunger,  and  thirft  of  animals,  thefe  motions  cf  vege- 
tables, in  doling  up  their  flowers,  muft  be  aferibed  to  thedifa- 
greeable  fenfation,  and  not  to  the  irritation  of  cold.  Others 
clofe  up  their  leaves  during  darknefs,  which,  like  tire  former, 
cannot  he  owing  to  irritation,  as  the  irritating  material  is 
withdrawn. 

The  approach  of  the  anthers  in  many  flowers  to  the  flag- 
mas , and  of  the  piftils  of  fome  flowers  to  the  anthers,  muft  be 
aferibed  to  the  paffion  of  love,  and  hence  belongs  to  fenfation, 
not  to  irritation. 

III.  That  the  vegetable  world  pouches  fome  degree  of  vo- 
luntary powers,  appears  from  their  neceffity  to  fieep,  which  we 
have  {hewn,  in  Sect.  XVIII.  to  eonhft  in  tire  temporary  aboli  - 
tion of  voluntary  power.  This  voluntary  power  feems  to  be 
exerted  in  the  circular  movement  ot  the  tendrils  of  vines,  and 
other  climbing  vegetables;  or  in  the  efforts  to  turn  the  upper 
furface  ot  their  leaves,  or  their  fhowers-to  the  light. 

IV.  The  alfociations  of  fibrous  motions  are  obfervable  in 
the  vegetable  world,  as  well  as  in  the  animal.  The  demons 
of  the  leaves  of  the  feniitive  plant  have  been  accuftomed  to  con- 
tra ft  at  the  lame  time  from  the  abfence  of  lftht ; hence,  if  by 
any  other  circumftance,  a.s  a flight  ftroke  01  injury,  one  diviV 
lion  is  irritated  into  contraction,  tire  neighbouring  ones  con- 

traft 


u OF  VEGETABLE  ANIMATION.  Sect.  XIII.  c. 

traff  alfo,  from  their  motions  being  affociated  with  thofe  of 
the  irritated  part.  So  the  various  ftamina  of  the  clafs  o fyn  - 
genefia  have  been  accuftomed  to  contract  together  in  the  even- 
ing, and  thence,  it  you  ftimulate  one  of  them  with  a pin,  ac- 
cording to  the  experiment  of  M.  Colvolo,  they  all  contract 
from  their  acquired  aflfoekrtions. 

Jo  evince  that  the  collapfmg  of  the  fenfitive  plant  is  no: 
owing  to  any  mechanical  vibrations  propagated  along  the  whole 
branch,  when  a fingle  leaf  is  ftrucJCwith  the  linger,  a leaf  of 
it  was  ftit  with  {harp  feiffors,  and  fome  feconds  of  time  palled 
before  the  plant  feemed  fenfible  of  the  injury;  and  then  the 
whole  branch  collapfed  as  far  as  the  principal  Item.  This  ex- 
periment was  repeated  feveral  times  with  tire  leaft  poflmle  im- 
pulfe  to  the  plant. 

V.  x.  For  the  numerous  circumftances  in  which  vegeta- 
ble buds  are  analogous  to  animals,  the  reader  is  referred  to  the 
additional  notes  at  the  end  of  the  Botanic  Garden,  Part  I.  I? 
is  there  (hewn,  that  the  roots  of  vegetables  referable  the  lac- 
teal fyflem  of  animals;  the  fap-veflels  in  the  early  fpring,  be- 
fore their  leaves  expand,  are  analogous  to  the  placenta! 
velfels  ot  the  Icetus ; that  the  leaves  of  land-plants  rcfemble 
lungs,  and  thofe  of  aquatic  plants  the  gills  of  fifh ; diet  there 
are  other  fyftetns  of  velfels  refembling  the  vena  portarum  of 
quadrupeds,  or  the  aorta  of  hlh ; that  the  digeflive  power  of 
vegetables  is  fimilar  to  that  of  animals  converting  the  fluids, 
which  drey  abforb  into  fugar ; that  their  feeds  referable  tire- 
eggs  of  animals,  and  their  buds  and  bulbs  their  viviparous  cff- 
ipring.  Atrd,  laftly,  that  the  anthers  and  itigmas  are  real 
animals,  attached,  indeed,  to  their  parent  tree,  like  polypi  or 
coral  infefts,  but  capable  of  fpantaneuus  motion ; that  they 
are  a tie  fled  with  the  paffion  of  love,  and  furniflied  with 
powers  of  re-producing  their  fpecies,  and  are  fed  with  honey 
like  the  moths  and  butterflies,  which  plunder  their  nectaries. 
See  Botanic  Garden,  Part  I.  add.  note  XXXIX. 

The  male  flowers  of  vallifneria  approach  Hill  nearer  to 
apparent  animality,  as  they  detach  themfeives  from  the  parent 
plant,  and  float  on  the  furtace  of  the  water  to  the  female  ones. 
Botanic  Garden,  Part  II.  art.  Vailifnerki.  Other  flowers,  of 
the  clafles  of  monecia  anddtecia,  and  polvgamia,  difeharge  the 
fecundating  ferina,  which,  floating  in  die  air,  ;s  carried  to  the 
flignru  of  the  female  flowers,  and  that  at  coniiderable  diflances. 
Can  this  be  affected  by  any  fpeciflc  attraction?  or.  like  the 
diffuuon  of  the  odorous  particles  ot  flowers,  is  it  left  to  the 
currents  of  winds,  and  the  accidental  mifear-riages  of  ic  coun- 
teracted bv  the  quantity  of  its  production  ? 

2.  This 


Sect.  XIII.  5.  OF  VEGETABLE  ANIMATION.  7 s 

2.  This  leads  us  to  a curious  enquiry,  whether  vegetables 
have  ideas  of  external  things  ? As  all  our  ideas  are  originally- 
received  by  our  fenfes,  the  queftion  may  be  changed  to,  whe- 
ther vegetables  poffefs  any  organs  of  feme  ? Certain  it  is,  that 
they  poffefs  a fenfe  of  heat  and  cold,  another  of  moifture  and 
drynefs,  and  another  of  light  and  darknefs ; ' for  they  clofe  their 
petals  occalionally  from  the  prefence  of  cold,  moifture,  or 
darknefs.  And  it  has  been  already  fhewn,  that  thefe  actions 
cannot  be  performed  limply  from  irritation,  becaufe  cold  and 
darknefs  are  negative  quantities,  and  on  that  account  fenfation 
or  volition  are  implied,  and,  in  confequence,  a fenforium  or 
union  of  their  nerves.  So  when  we  go  into  the  light,  we 
contrail  the  iris ; not  from  any  ftimulus  of  the  light  on  the  fine 
mufcles  of  the  iris,  but  from  its  motions  being  affociated  with 
the  fenfation  of  too  much  light  on  the  retina,  which  could 
not  take  place  without  a fenforium  or  centre  of  union  of  the 
nerves  of  the  iris  with  thofe  of  vilion.  See  Botanic  Garden, 
Part  I.  Canto  3.  1.  440,  note. 

Belides  thefe  organs  of  fenfe,  which  diflinguifh  cold,  moif- 
ture, and  darknefs,  the  leaves  of  mimofa,  and  of  dionaea,  and 
of  drolera,  and  the  ftamens  of  many  flowers,  as  of  the  berber- 
ry, and  the  numerous  clafs  of  fyngenefla,  are  fenfible  to  me- 
chanic impait ; that  is,  they  poffefs  a fenfe  of  touch,  as  well  as 
a common  fenforium ; by  the  medium  of  which  their  mufcles 
are  excited  into  aCtion.  Laftly,  in  many  flowers  the  anthers, 
when  mature,  approach  the  ftigma  ; in  others  the  female  or- 
gan approaches  to  the  male.  In  a plant  of  collinfonia,  a 
branch  of  which  is  now  before  me,  the  two  yellow  ftamens 
are  about  three  eighths  of  an  inch  high,  and  diverge  from  each 
other,  at  an  angle  of  about  fifteen  degrees ; the  purple  ftyle  is 
half  an  inch  high,  and  in  fome  flowers  is  now  applied  to  tire 
ftamen  on  the  right  hand,  and  in  others  to  that  of  the  left ; and 
will,  I fuppofe,  change  place  to-morrow  in  thofe  where  the  an- 
thers have  not  yet  effufed  their  power. 

I afk,  by  what  means  are  the  anthers  in  many  flowrers,  and 
ftigmas  in  other  flowers,  directed  to  find  their  paramours  ? 
How"  do  either  of  them  know  that  the  other  exifts  in  their  vi- 
cinity ? Is  this  curious  kind  of  florge  produced  by  mechanic 
attraction,  or  by  the  fenfation  of  love?  The  latter  opinion  is 
fupportedby  the  ftrongeft  analogy,  becaufe  a re-produ£tion  of 
the  fpecies  is  the  confequence ; and  then  another  organ  of  fenfe 
muft  be  wanted  to  direCt  thefe  vegetable  amourettes  to  find 
each  other,  one  probably  analogous  to  our  fenfe  of  fmell, 
which  in  the  animal  world  direCts  the  new-born  infant  to  its 
fource  of  nourifhment,  and  they  may  thus  poffefs  a faculty  of 
perceivirtg  as  well  as  of  producing  odours. 

M 


Thus 


7'6  PRODUCTION. OF  IDEAS.  Sect.  XIV.  i. 

Thus,  befides  a kind  of  tafte  at  the  extremities  of  their 
roots,  iknilar  to  that  of  the  extremities  of  our  ladteal  veffels, 
for  the  purpofe  of  felecting  their  proper  food;  and  befides 
different  kinds  of  irritability  reliding  in  the  various  glands, 
which  feparate  honey,  wax,  refin,  and  other  juices  from  their 
blood  ; vegetable  life  feems  to  poffcfs  an  organ  of  fenfe  to  dif- 
tinguifh  the  variations  of  heat,  another  to  diftinguifh  the  va- 
rying degrees  of  moifture,  another  of  light,  another  of  touch, 
and  probably  another  analogous  to  our  fenfe  of  fmell.  To 
thefe  muft  be  added  the  indubitable  evidence  of  their  paffion  of 
love ; and  I think  we  may  truly  conclude,  that  they  are  furniih- 
ed  with  a common  fenforium  belonging  to  each  bud,  and  that 
they  mull;  occafionally  repeat  thofe  perceptions  either  in  their 
dreams  or  waking  hours,  and  confequently  poffefs  ideas  of  fo 
many  of  the  properties  of  the  external  world,  and  of  their  own 
exiftence. 


SECT.  XIV. 

OF  THE  PRODUCTION  OF  IDEAS. 

I.  Of  material  and  immaterial  beings.  Doftrinc  of  St. 
Paul.  II.  I.  Of  the  fenfe  of  touch.  Of  fclidity. 
1.  Of  figure,  Motion.  Time.  Place.  Space.  Number. 
3-  Of  the  penetrability  of  matter.  4.  Spirit  of  ani- 
mation pofifeffes  folidity,  figure,  vifibility,  (sic.  Of  fipi- 
rits  and  angels.  5.  The  exiftence  of  external  things. 
III.  Of  vijion.  IV;  Of  hearing.  V.  Of  fmell  and 
tafle.  VI.  Of  the  organ  of  fenfe  by  which  we  perceive 
heat  and  cold,  not  by  the  fenfe  of  touch.  VII.  Of  the 
fenfe  of  extenfion-,  the  whole  of  the  locomotive  mu  files  . 
may  be  confidercd  as  one  organ  of  fenfe.  VIII.  Of  the 
fciifies  of  hunger , thirfi , want  of  frcjh  air,  fuckling  chil- 
dren, and  lufi.  IX.  Of  many  other  organs  of  fenfe  be- 
longing to  the  glands.  Of  painful  fenfaticns  from  the 
excefs  of  light , preffure , heat , itching , cauflics,  and 
electricity. 

I.  PHILOSOPHERS  have  been  much  perplexed  to  under- 
hand, in  what  manner  we  become  acquainted  with  the  exter- 
nal world;  infomuch  that  Dr.  Berkly  even  doubted  its  exig- 
ence, from  having  obferved,  (as  he  thought)  that  none  of  our 
ideas  refemble  their  correfpondent  objects.  Mr.  Hume  afferts, 
that  our  belief  depends  on  the  greater  diftindlnefs  or  energy  qf 
our  ideas  from  perception ; and  Mr-  Reid  has  lately  contended. 


Sect.  XIV.  2.  PRODUCTION  OF  IDEAS. 


7,7 

that  our  belief  of  external  objeds  is  an  innate  principle,  necef- 
farjly  joined  with  our  perceptions. 

So  true  is  the  obfervation  of  the  famous  Malbranch,  “ that 
our  fenfes  are  not  given  us  to  difcover  the  eifences  of  things, 
but  to  acquaint  us  with  the  means  of  preferving  our  exiftence,” 
(L.  I.  ch.  v.)  a melancholy  reflection  to  philofophers  ! 

Some  philofophers  have  divided  all  created  beings  into  ma- 
terial and  immaterial:  the  former  including  all  that  part  of  be- 
ing, which  obeys  the  mechanic  laws  of  adion  and  re-adion, 
but  which  can  begin  no  motion  of  itfelf;  the  other  is  the  caufe 
of  all  motion,  and  is  either  termed  the  power  of  gravity,  or  of 
fpecific  attraction,  or  the  fpirit  of  animation.  This  immate- 
rial agent  is  fuppofed  to  exift  in  or  with  matter,  but  to  ne  quite 
diftind  from  it,  and  to  be  equally  capable  of  exiftence,  after 
the  matter,  which  now  poffeffes  it,  is  decompofed. 

Nor  is  this  theory  ill  fupported  by  analogy,  fince  heat, 
■eleCtricity,  and  magnetifm  can  be  given  to  or  taken  from  a 
■piece  of  iron;  and  muft  therefore  exift,  whether  feparated 
from  the  metal,  or  combined  with  it.  From  a parity  of  rea- 
foning,  the  fpirit  of  animation  would  appear  to  be  capable  of 
exifting  as  well  feparately  from  the  body  as  with  it. 

I beg  to  be  underftood,  that  I do  not  with  to  difpute  about 
words,  and  am  ready  to  allow,  that  the  powers  of  gravity, 
fpecific  attraction,  eledricity,  .magnetifm,  and  even  the  fpirit 
of  animation,  may  confift  of  matter  of  a finer  kind ; and  to 
believe,  with  St.  Paul  and  Malbranch,  that  the  ultimate  caufe 
only  of  all  motion  is  immaterial,  that  is,  God.  St.  Paul  fays, 
“ in  him  we  live,  and  move,  and  have  our  being;”  and,  in 
the  15th  chapter  of  the  Corinthians,  diftinguifhes  between 
the  pfyche  or  living  fpirit,  and  the  pneuma  ©r  reviving  fpirit. 
By  the  words  fpirit  of  animation  or  fenforial  power,  I mean 
«niy  that  animal  life  which  mankind  poflefTes  in  common 
with  brutes,  and  in  fome  degree  even  with  vegetables,  and 
leave  the  confideration  of  the  immortal  part  of  us,  which  is 
the  objeCl  of  religion,  to  dnofe  who  treat  of  revelation. 

II.  J.  Of  the  Senfe  of  Touch. 

The  firft  ideas  we  become  acquainted  with,  are  thofe  of  the 
fenfe  of  touch ; for  the  foetus  muft  experience  fome  varieties  of 
agitation,  and  exert  fome  mufcular  adion,  in  the  womb;  and 
may,  with  great  probability,  be  fuppofed  thus  to  gain  fome  ideas 
■of  its  own  figure,  of  that  of  the  uterus,  and  of  the  tenacity  of 
the  fluid  that  lurrounds  it,  (as  appears  from  the  fads  mention- 
ed in  the  fucceeding  Sedion  upon  Inftind.) 

Many  of  the  organs  of  fenfe  are  confined  to  a final!  part  of 

the 


PRODUCTION  OF  IDEAS.  Sect.  XIV.  2. 


The  body,  as  the  noflrils,  ear  or  eye,  whilfl  the  fenfe  of  touch 
is  difFufed  over  the  whole  fkin,  but  exifts,  with  a more  exqui- 
fite  degree  of  delicacy,  at  the  extremities  of  the  fingers  and 
thumbs;  and  in  the  lips.  The  fenfe  of  touch  is  thus  very  com- 
modioufly  difpofed,  for  the  purpofe  of  encompafling  fmaller  bo- 
dies, and  for  adapting  itfelf  to  the  inequalities  of  larger  ones. 
The  figure  of  finall  bodies  feems  to  be  learnt  by  children  by 
their  lips  as  much  as  by  their  fingers  ; on  which  account  they 
put  every  new  objedb  to  their  mouths,  when  they  are  fatiated 
with  food,  as  well  as  when  they  are  hungry.  And  puppies 
feetn  to  learn  their  ideas  of  figure  principally  by  the  lips  in 
their  mode  of  play. 

We  acquire  our  tangible  ideas  of  objects  either  by  the  fim- 
ple  preffure  of  this  organ  of  touch  againft  a folid  body,  or  by 
moving  our  organ  of  touch  along  the  furface  of  it:  in  the  for- 
mer cafe,  we  learn  the  length  and  bieadth  of  the  objcdf  by  the 
quantity  of  our  organ  of  touch  that  is  impreffed  by  it : in  the 
latter  cafe,  we  learn  the  length  and  breadth  of  objedts  by  the 
continuance  of  their  preffure  on  our  moving  organ  of  touch. 

It  is  hence  that  we  are  very  flow  in  acquiring  our  tangible 
ideas,  and  very  flow  in  recolledfing  them  ; for  it  I now  think 
of  the  tangible  idea  of  a cube,  that  is,  if  I think  of  its  figure, 
I rnuft  conceive  myfelf  as  pafling  my  fingers  over  it,  and  feem 
in  fome  meafure  to  feel  die  idea,  as  I formerly  did  the  impref- 
fion  at  the  ends  of  them,  and  am  thus  very  flow  in  diftindfly 
recolledfing  it. 

When  a body  compreffes  any  part  of  our  fenfe  of  touch, 
what  happens  ? Firfl,  this  part  of  our  fenforium  undergoes  a 
mechanical  compreflion,  which  is  termed  a ftimulus  ; fecond- 
ly,  an  idea,  or  contradbion  of  a part  of  die  organ  of  fenfe,  is 
excited;  thirdly,  a motion  of  the  central  parts,  or  of  the 
whole  fenforium,  which  is  termed  fenfarion,  is  produced ; and 
thefe  three  conftitute  the  perception  of  folidity. 

2.  Figure , Motion , Time , Place,  Space , Number. 

No  one  will  deny,  that  the  medulla  of  the  brain  and  nerves 
lias  a certain  figure ; which,  as  it  is  difFufed  through  nearly 
the  whole  of  die  body,  mud  have  nearly  the  figure  of  that 
body.  Now  it  follows,  that  the  fpirit  of  animation,  or  living 
principle,  as  it  occupies  this  medulla,  and  no  other  part, 
(which  is  evinced  by  a great  variety  of  cruel  experiments  on 
living  animals)  it  follows,  that  dais  fpirit  of  animation  has 
alfo  the  fame  figure  as  the  medulla  above  delcribed.  I appeal 
to  common  fenfe ! the  fpirit  of  animation  adds ; where  does 
it  adt  ? It  adds  wherever  there  is  the  medulla  above  mentioned ; 

and 


79 


Sect.  XIV.  2.  PRODUCTION  OF  IDEAS. 

and  that  whether  the  limb  is  yet  joined  to  a living  animal,  or 
whether  it  be  recently  detached  from  it ; as  the  heart  of  a viper 
or  frog  will  renew  its  contra&ions,  when  pricked  with  a pin, 
for  many  minutes  of  time  after  its  exfedtion  from  the  body.— 
Does  it  a6t  any  where  elfe  ? No ; then  it  certainly  exifts  in  this 
part  of  fpace,  and  no  where  elfe ; that  is,  it  hath  figure ; name- 
ly, the  figure  of  the  nervous  fyftem,  which  is  nearly  the  figure 
of  the  body.  When  the  idea  of  foliditv  is  excited,  as  above 
explained,  a part  of  theextenfive  organ  of  touch  is  comprefled 
by  fome  external  body;  and  this  part  of  the  fenforium  fo  com- 
preffed,  exactly  refembles  in  figure , the  figure  of  the  body  that 
comprefled  it.  Hence,  when  we  acquire  the  idea  of  foiidity, 
we  acquire,  at  the  fame,  the  idea  of  figure  ; and  this  idea  of 
figure,  or  motion  of  a part  of  the  organ  of  touch,  exactly  re- 
fembles, in  its  figure , the  figure  of  the  body  that  occafions  it  , 
and  thus  exadfly  acquaints  us  with  this  property  of  the  exter- 
nal world. 

Now,  as  the  whole  univerfe,  with  all  its  parts,  pofiefles  a 
certain  form  or  figure,  if  any  part  of  it  moves,  that  form  or 
figure  of  the  whole  is  varied:  hence,  as  motion  is  no  other 
than  a perpetual  variation  of  figure,  our  idea  of  motion  is  alfo 
a real  refemblance  of  the  motion  that  produced  it. 

It  may  be  faid,  in  objedlion  to  this  definition  of  motion,  that 
an  ivory  globe  may  revolve  on  its  axis,  and  that  here  will  be  a 
motion  without  change  of  figure.  But  the  figure  of  the  parti- 
cle x on  one  fide  of  this  globe,  is  not  the  fiame  figure  as  the 
figure  of  y on  the  other  fide,  any  more  than  the  particles  them- 
felves  are  the  fame,  though  they  are  fimilar  figures  ; and  hence 
they  cannot  change  place  with  each  other,  without  difturbing 
or  changing  the  figure  of  the  whole. 

Our  idea  of  time  is  from  the  fame  fource,  but  is. more  ab- 
ftradfed,  as  it  includes  only  the  comparative  velocities  of  thefe 
variations  of  figure hence,  if  it  be  afked,  how  long  was  this 
book  in  printing  ? it  may  be  anfwered,  whilft  the  fun  was  paf- 
fing  through  Aries. 

Our  idea  of  place  includes  only  the  figure  of  a group  of 
bodies,  not  the  figure  of  the  bodies  themfelves.  If  it  be  slic- 
ed, where  is  No'ttinghamfhire  ? the  anfwer  is,  it  is  furrounded 
by  Derbyfhire,  Lincolnfliire,  and  Leicefterfhire : hence  place 
is  our  idea  of  the  figure  of  one  body  furrounded  by  the  figures 
of  other  bodies. ' 

- The  idea  of  space  is  a more  abftracffed  idea  of  place  ex- 
cluding the  group  of  bodies. 

The  idea  of  number  includes  only  the  particular  arrange- 
ments, or  diftributions  of  * group  of  bodies,  and  is  therefore 
; " 1 . only 


So 


PRODUCTION  OF  IDEAS.  Sect.  XIV.  2. 


only  a more  abftracted  idea  of  the  parts  of  tire  figure  of  the 
group  of  bodies : thus,  when  I fay  England  is  divided  into  forty 
counties,  I only  fpeak  of  certain  divifions  of  its  figure. 

Hence  arifes  the  certainty  of  the  mathematical  fciences,  as 
they  explain  thefe  properties  of  bodies,  which  are  exactly  re- 
fembled  by  our  ideas  of  them,  whilft  we  are  obliged  to  col- 
led! almoft  all  our  other  knowledge  from  experiment ; that  is, 
by  obferving  the  effects  exerted  by  one  body  upon  anodier. 

3.  Of  the  Penetrability  cf  Matter. 

The  impoffibilily  of  two  bodies  .exifting  together,  in  the 
fame  fpace,  cannot  be  deduced  from  our  idea  of  folidity,  or  of 
figure.  As  foon  as  we  perceive  the  motions  of  objects  that 
furround  us,  and  learn  that  we  .poflefs  a power  to  move  our 
own  bodies,  we  experience,  that  thofe  -objects,  which  excite 
in  us  the  idea  of  folidity  and  of  figure,  oppofe  this  voluntary 
movement  of  our  own  organs;  as  whilft  I endeavour  to 
oomprefs  between  my  hands  an  ivory  ball  into  a fpheroid. 
And  we  are  hence  taught  by  experience,  tixat  our  own  body, 
and  thofe  which  we  touch,  cannot  exift  in  the  fame  part  of 
fpace. 

But  this  by  no  means  demonftrates,  that  no  two  bodies  can 
exift  together  in  the  fame  part  cf  fpace.  Galiiaeo,  in  the  pre- 
face to  his  works,  feems  to'  be  of  opinion,  that  matter  is  nor 
impenetrable.  Mr. .Michel,  and  Mr.  Bofcowich,  in  his  Theo- 
ria.  Philof.  Natur.  have  efpoufed  this  hypothefis : which  has 
been  lately  published  bv  Dr.  Prieftley,  to  whom  the  world  is 
much  indebted  for  fo  many  important  difeoveries  in  fcience. 
(Hift.  of  Light  and  Colours,  p.  391.)  The  uninterrupted 
puflage  of  light  through  tranfparent  bodies,  of  the  eledtric 
jether  through  metallic  and  aqueous  bodies,  and  of  the  magnetic 
effluvia  through  all  bodies,  would  feem  to  give  fome  probabi- 
lity to  this  opinion.  Hence  it  appears,  that  beings  may  exift 
without  pofleffing  the  property  of  folidity,  as  well  as  they  can 
exift  without  polleffing  the  properties  which  excite  our  fmell 
or  tafte,  and  can  thence  occupy  fpace  without  detruding  other 
bodies  from  it;  but  we  cannot  become  acquainted  with  fuch 
beings  by  our  fenfe  of  touch,  any  more  than  we  can  with 
odours  or  flavours  without  our  fenfes  of  fmell  and  tafte. 

But  that  any  being  can  exift  without  exifting  in  fpace,  is  to 
mv  ideas  utterly  incomprehenfible.  My  appeal  is  to  common 
fenfe.  To  be  implies  a when  and  a where ; the  one  is  com- 
paring it  with  the  motions  of  other  beings,  and  the  other  with 
their  fituations. 

If  there  was  but  one  objedl,  as  the  whole  creation  may  be 

confide  red 


Sect. XIV.  2.  PRODUCTION  OF  IDEAS.  Si 

eonfidered  as  one  object,  then  I cannot  afk  where  it  exifts  ? 
for  there  are  no  other  objects  to  compare  its  htuation  with. 
Hence,  if  any  one  denies  that  a being  exifts  in  fpace,  he  de- 
nies that  there  are  any  other  beings  but  that  one  ; for  to  an- 
fwer  the  queflion,  “ Where  does  it  exifti”  is  only  to  men- 
tion the  lituation  of  the  objects  that  lurround  it. 

In  the  fame  manner,  if  it  be  afked,  “ When  does  a being 
exift;?”  the  anfvver  only  jpecihes  the  fucceffive  motions  ei- 
ther of  itfelf,  or  of  other  bodies : hence,  to  fay  a body  exifts 
not  in  time,  is  to  fay,  that  there  is,  or  was,  no  motion  in  the 
world. 

4.  Of  the  Spirit  of  Animation. 

But  though  there  may  exift  beings  in  the  univerfe,  that  have 
not  the  property  of  folidity ; that  is,  which  can  poffefs  any 
part  of  fpace,  at  the  fame  time  that  it  is  occupied  by  other  bo- 
dies ; yet  there  may  be  other  beings  diat  can  aftume  this  pro- 
perty of  folidity,  or  difrobe  themielves-of  it  occaftonally,  as 
we  are  taught  of  lpirits,  and  of  angels ; and  it  would  leem, 
that  the  spirit  of  animation  muft  be  endued  with  this 
property,  otherwife  how  could  it  occaiionally  give  motion  to 
the  limbs  of  animals  ? — or  be  itfelf  ftimulated  into  motion  by 
the  obtruftons  of  furrounding  bodies,  as  of  light,  or  odour  ? 

If  the  fpirit  of  animation  was  always  neceffarily  penetrable, 
it  could  not  influence  or  be  influenced  by  the  folidity  of  mat- 
ter ; they  would  exift  together,  but  could  not  detrude  each  other , 
from  the  part  of  fpace  where  they  exift ; that  is,  they  could  not 
communicate  motion  to  each  other.  No  two  things  can  influ- 
ence or  affeft  each  other,  which  have  not  feme  property  com- 
mon to  both  of  them-,  for,  to  influence  or  affedl  another  body, 
is  to  give  or  communicate  fome  property  to  it,  that  it  had  not 
before;  but  how  can  one  body  give  that  to  another  which  it 
does  not  poffefs  itfelf? — The  words  imply,  that  they  muft 
agree  in  having  the  power  or  faculty  of  pofleffing  fome  com- 
mon property.  Thus,  if  one  body  removes  another  from  the 
part  of  fpace  that  it  poffeffes,  it  muft  have  the  power  of  occu- 
pying that  fpace  itfelf:  and  if  one  body  communicates  heat  or 
motion  to  another,  it  follows,  that  they  have  alike  the  property 
of  pofleffing  heat  or  motion. 

Hence,  the  fpirit  of  animation,  at  the  time  it  communicates 
or  receives  motion  from  folid  bodies,  muft  itfelf  poflefs  fome  pro- 
perty of  folidity.  And  in  confequence,  at  the  time  it  receives 
other  kinds  of  motion  from  light,  it  muft  poffefs  that  property 
which  light  poffeffes,  to  communicate  that  kind  of  motion  ; and 
for  which  no  language  has  a name,  unlefs  itmav  be  termed  Vif'I- 

bilitv. 


82 


PRODUCTION  OF  IDEAS.  Sect.  XIV.  2. 


bility.  And,  at  the  time  it  is  ftimulated  into  other  kinds  of  ani- 
mal motion,  by  the  particles  of  fapid  and  odorous  bodies  affect- 
ing the  fenles  of  tafte  and  fmell,  it  mu  ft  refemble  thefe  particles 
of  flavour,  and  of  odour,  in  poffeding  fome  fimilar  or  corref- 
pondent  property ; and  for  which  language  has  no  name,  un- 
lefs  we  may  ufe  the  words  Saporofity  and  Odorofity  for  thofe 
common  properties  which  are  poffefTed  by  our  organs  of  taft£ 
and  fmell,  and  by  the  particles  of  fapid  and  odorous  bodies  ; as 
the  words  Tangibility  and  Audibility  may  poffefs  die  common 
property  poffefTed  by  our  organs  of  touch,  and  of  hearing,  and 
by  the  lolid  bodies,  or  their  vibrations,  which  affedt  thofe 
organs. 

5.  Finally,  though  the  figures  of  bodies  are  in  truth  refem- 
bled  by  the  figure  of  the  part  of  the  organ  ot  touch,  which  is 
ftimulated  into  motion  ; and  that  organ  relembles  the  folid  bo- 
dy which  ftimulates  it,  in  its  property  of  folidity ; and  though 
the  fenfe  of  hearing  refembles  the  vibrations  of  external  bo- 
dies, in  its  capability  of  being  ftimulated  into  motion  by  thole 
vibrations ; and  though  our  other  organs  of  fenfe  refemble  the 
bodies  that  ftimulate  them,  in  their  capability  of  being  ftimu- 
lated by  them ; and  we  hence  become  acquainted  with  thefe 
properties  of  the  external  world;  yet,  as  we  can  repeat  all  thefe 
motions  of  our  organs  of  fenfe  by  the  efforts  of  volition,  or 
in  confequence  of  the  fenfation  of  pieafure  or  pain,  or  by  their 
affociation  with  other  fibrous  motions,  as  happens  in  our  reve- 
ries or  in  fleep,  there  would  ftill  appear  to  be  fome  difficulty 
in  demonftrating  the  exiftence  of  any  thing  external  to  us. 

In  our  dreams  we  cannot  determine  this  circumftance,  bc- 
caufe  our  power  of  volition  is  iufpended,  and  the  ltimuli  ot 
external  objedts  are  excluded  ; but  in  our  waking  hours  we 
can  compare  our  ideas  belonging  to  one  fenfe,  with  thofe  be- 
longing to  another,  and  can  thus  diftinguiih  the  ideas  occa- 
fioned  by  irritation,  from  thofe  excited  by  fenlation,  volition, 
or  afTociation.  Thus,  if  the  idea  of  the  fweetnefs  of  iugar 
ftrould  be  excited  in  our  dreams,  the  whitenefs  and  hardnels 
of  it  occur  at  the  fame  time  by  affociation  ; and  we  believe 
a material  lump  of  fugar  prelent  before  us.  But  if,  in  our 
waking  hours,  the  idea  of  the  fweetnels  ot  fugar  occurs  to 
us,  the  ftimuli  of  furrounding  objedts,  as  the  edge  of  the  table 
on  which  we  prefs,  or  green  colour  ot  the  grafs  on  which 
we  tread,  prevent  the  other  ideas  of  the  hardnels  and  white  - 
nefs  of  the  fugar  from  being  exerted  by  affociation.  Or  it 
they  fhould  occur,  we  voluntarily  compare  them  with  the  ir- 
ritative ideas  of  the  table  or  grafs  above  mentioned,  and  detect 
their  fallacy.  We  can  thus  diftinguiih  the  ideas  caufed  by. 


Sect.  XIV.  3.  PRODUCTION  OF  IDEAS.  83 

the  ftimuli  of  external  objcdls,  from  thofe  which  are  introduc- 
ed by  affociation,  fenfation,  or  volition ; and  during  our  wak- 
ing hours,  can  thus  acquire  a knowledge  of  the  external 
world.  Which,  neverthelefs,  we  cannot  do  in  our  dreams, 
becaufe  we  have  neither  perceptions  of  external  bodies,  nor 
the  power  of  volition,  to  enable  us  to  compare  them  with  the 
ideas  of  imagination. 

III.  OfVifion . 

Our  eyes  obferve  a difference  of  colour,  or  of  fhade,  in  the 
prominences  and  depreffion  of  objedls,  and  that  thofe  fhades 
uniformly  vary,  when  the  fenfe  of  touch  obferves  any  varia- 
tion. Hence,  when  the  retina  becomes  ftimulated  by  colours 
or  fhades  of  light  in  a certain  form,  as  in  a circular  fpot,  we 
know  by  experience,  that  this  is  a fign,  that  a tangible  body  is 
before  us  ; and  that  its  figure  is  refembled  by  the  miniature  fi- 
gure of  the  part  of  the  organ  of  vition  that  is  thus  ftimulated. 

Here,  whilft  the  ftimulated  part  of  the  retina  relembles  ex- 
actly the  viftble  figure  of  the  whole  in  miniature,  the  various 
kinds  of  ftimuli  form  different  colours,  mark  the  viftble  figures 
of  the  minuter  parts ; and,  by  habit,  we  inftantly  recall  the  tan* 
gible  figures. 

Thus,  when  a tree  is  the  objedt  of  fight,  a part  of  the  reti- 
na, refembling  a flat  branching  figure,  is  ftimulated  by  vari- 
ous fhades  of  colours  ; but  it  is  by  fuggeftion,  that  the  gibbo- 
ftty  of  the  tree,  and  the  mofs  that  fringes  its  trunk,  appear  be- 
fore us.  Thefe  are  ideas  of  fuggeftion,  which  we  feel  or  at- 
tend to,  affociated  with  the  motions  of  the  retina,  or  irritative 
ideas,  which  we  do  not  attend  to. 

So  that,  though  our  viftble  ideas  refemble  in  miniature  the 
outline  of  the  figure  of  coloured  bodies,  in  other  refpedfs  they 
ferve  only  as  a language,  which,  by  acquired  affociations,  in- 
troduce the  tangible  ideas  of  bodies.  Hence  it  is,  that  this 
fenfe  is  fo  readily  deceived  by  the  art  of  the  painter,  to  our 
amufement  and  inftrudlion.  The  reader  will  find  much  very 
curious  knowledge  on  this  fubjedl,  in  Bifhop  Berkley’s  Effay 
on  Vifion,  a work  of  great  ingenuity. 

The  immediate  objedt,  however,  of  the  fenfe  of  vificn,  is 
light ; this  fluid,  though  its  velocity  is  fo  great,  appears  to  have 
no  preceptible  mechanical  impulfe,  as  was  mentioned  in  the 
third  Sedtion,  but  feems  to  ftimulate  the  retina  into  animal 
motion  by  its  tranfmiflion  through  this  part  of  the  fenforium: 
for  though  the  eyes  of  cats  or  other  animals  appear  luminous 
in  obfcure  places,  yet  it  is  probable,  that  none  of  the  light, 
which  falls  on  the  retina,  is  refledted  from  it,  but  adheres  to  or 
enters  into  combination  with  the  choroide  coat  behind  it. 

N 


The 


84  PRODUCTION  OF  IDEAS.  Sect.  XIV.  4. 

The  combination  of  die  particles  of  light  with  opake  bo- 
dies, and  therefore  with  the  choroide  coat  of  the  eve,  is  evinc- 
ed from  the  heat,  which  is  given  out,  as  in  other  chemical 
combinations.  For  the  fun  beams  communicate  no  heat  in 
their  paflfage  through  tranfparent  bodies,  with  which  they  do 
not  combine,  as  the  air  continues  cool  even  in  the  focus  of 
the  largeft  burning -glaffes,  which  in  a moment  vitrifies  a par- 
ticle of  opaque  matter. 

IV.  Of  the  Organ  of  Hearing. 

It  is  generally  believed,  that  the  tympanum  of  the  ear  vi- 
brates mechanically,  when  expofed  to  audible  founds,  like  the 
firings  of  one  mulical  inflrument,  when  the  fame  notes  arc 
flruck  upon  another.  Nor  is  this  opinion  improbable,  as  the 
rnufcles  and  carrileges  of  the  lyranx  are  emploved  in  produc- 
ing variety  of  tones  by  mechanical  vibration  : fo  the  rnufcles 
and  bones  of  the  ear  feem  adapted  to  increafe  or  diminifh  the 
tendon  of  the  tympanum,  for  the  purpofes  of  fimilar  mecha- 
nical vibrations. 

But  it  appears  from  diflfecfion,  that  tire  tympanum  is  not  the 
immediate  organ  of  hearing,  but  that,  like  the  humours  and 
cornea  of  the  eye,  it  is  only  of  ufe  to  prepare  the  objedf  for 
tire  immediate  organ.  For  the  portio  mollis  of  the  auditory 
nerve  is  not  fpread  upon  the  tympanum,  but  upon  the  viflibu- 
lum,  and  cochlea,  and  femicircular  canal  of  the  ear ; while, 
between  the  tympanum  and  the  expaniion  of  the  auditory  nerve, 
the  cavity  is  laid,  by  Dr.  Cotunnus  and  Dr.  Meckel,  to  be 
filled  with  water ; as  they  had  frequently  obferved  by  freezing 
the  heads  of  dead  animals  before  they  di  fleeted  them;  and  wa- 
ter being  a more  denfe  fluid  than  air,  is  much  better  adapted  to 
the  propagation  of  vibrations.  We  may  add,  that  even  the 
external  opening  of  the  ear  is  not  abfolutely  neceflary  for  the 
perception  of  found  : for  fome  people  who,  from  thefe  defeats, 
would  have  been  completely  deaf,  have  diftinguiflied  acute  or 
grave  founds  bv  the  tremours  of  a flick  held  between  their 
teeth,  propagated  along  the  bones  of  the  head.  (Haller.  Phyf. 
T.V.  p.295.) 

Hence  it  appears,  that  the  immediate  organ  ot  hearing  is  not 
affedted  by  the  particles  of  the  air  themfelves,  but  is  ftimuiated 
into  animal  motion  by  the  vibrations  of  them.  And  it  is  pro- 
bable, from  the  loofe  bones  which  are  found  in  the  heads  of 
fome  fifties,  that  the  vibrations  of  water  are  fenfibie  to  the  in- 
habiants  of  that  element  by  a fimilar  organ. 

The  motions  of  the  atmofphere,  which  we  become  acquaint- 
ed with  by  the  fenfe  of  touch,  are  combined  with  its  folidity, 

weight, 


Sect.  XIV.  5.  PRODUCTION  OF  IDEAS.  8,5 

weight,  or  vis  inertias;  whereas  thofe  that  are  perceived  by 
this  organ  depend  alone  on  its  elafticity.  But  though  the  vi- 
brati  jn  of  the  air  is  the  immediate  objedt  of  the  fenfe  of  hear- 
ing, yet  the  ideas  we  receive  by  this  fenfe,  like  thole  received 
from  light,  are  only  as  a language,  which,  by  acquired  aiToci- 
ations,  acquaints  us  with  thofe  motions  of  tangible  bodies 
which  depend  on  their  elafticity,  and  which  we  had  before 
{earned  by  our  fenfe  of  touch. 

V,  Of  Smell  and  of  Tafe. 

The  objedfs  of  fmell  are  diiTolved  in  the  fluid  atmofphere, 
and  thofe  of  tafte  in  the  faliva,  or  other  aqueous  fluid,  for  the 
better  defuflng  them  on  their  refpedtive  organs,  which  feem  to 
be  ftimulated  into  animal  motion,  perhaps  by  the  chemical  af- 
finities of  thefe  particles,  which  conftitute  the  fapidity  and 
odorofiiy  of  bodies  with  the  nerves  of  fenfe,  which  perceive 
them. 

Mr.  Volta  has  lately  obferved  a curious  circumftance  rela- 
tive to  our  fenfe  of  tafte.  If  a bit  of  clean  lead  and  a bit  of 
clean  lilver  be  feparately  applied  to  the  tongue  and  palate,  no 
tafte  is  perceived  ; but  by  applying  them  in  contadf,  in  refpedt 
to  the  parts  out  of  the  mouth,  and  nearly  fo  in  refpedt  to  the 
parts  which  are  immediately  applied  to  the  tongue  and  palate, 
a faline  or  acidulous  tafte  is  perceived,  as  of  a fluid  like  a itream 
of  eledtricity  palling  from  one  of  them  to  the  other.  This 
new  application  of  the  fenfe  of  tafte  deferves  further  inveftiga- 
tion,  as  it  may  acquaint  us  with  new  properties  of  matter. 

From  the  experiments  above  mentioned  of  Galvani,  Volta, 
Fowler,  and  others,  it  appears,  that  a plate  of  zinc  and  a plate 
of  lilver  have  a greater  eftedt  than  lead  and  lilver.  If  one  edge 
of  a plate  of  lilver,  about  the  lize  of  half  a crown  piece,  be 
placed  upon  the  tongue,  and  one  edge  of  a plate  of  zinc,  about 
the  fame  lize,  beneath  the  tongue,  and  if  their  oppofite  edges 
are  then  brought  into  contadf  before  the  point  of  the  tongue,  a 
tafte  is  perceived  at  the  moment  of  their  coming  into  contadf  : 
fecondly,  if  one  of  the  above  plates  be  put  between  the  upper 
lip  and  the  gum  of  the  fore-teeth,  and  the  other  be  placed  under 
the  tongue,  and  their  exterior  edges  be  then  brought  into  con- 
tadf in  a darkifh  room,  a flalh  of  light  is  perceived  in  the  eyes. 

Thefe  etfedfs,  I imagine,  only  Ihew  the  fenfibility  of  our 
nerves  of  fenfe,  to  very  fmall  quantities  of  the  eledfric  fluid, 
as  it  pafles  through  them  ; for  I fuppofe  thele  fenfations  are  oc- 
cafioned  by  flight  eledfric  Ihocks,  produced  in  the  following 
manner.  By  the  experiments  publiflied  by  Mr.  Benner,  with 
his  ingenious  doubler  of  eledtricity,  which  is  the  greatelf  dif- 

covery 


86 


PRODUCTION  OF  IDEAS.  Sect.  XIV  6. 


coverv  made  in  that  fcience  fmce  the  coated  jar,  and  the  educ- 
tion of  lightning  from  the  (kies,  it  appears  that  zinc  was  always 
found  minus,  and  filver  was  always  found  plus,  when  both  of 
them  were  in  their  feparate  ftate.  Hence,  when  they  are 
placed  in  the  manner  above  defcribed,  as  foon  as  their  exterior 
edges  come  nearly  into  contact,  fo  near  as  to  have  an  extreme- 
ly thin  plate  of  air  between  them,  that  plate  of  air  becomes 
charged  in  the  fame  manner  as  a plate  of  coated  glafs;  and  is, 
at  the  fame  inftant,  difcharged  through  the  nerves  of  tafte  or 
of  fight,  and  gives  the  fenfations,  as  above  defcribed,  of  light 
or  of  faporocity  ; and  only  Ihews  the  great  fenfibility  of  thefe 
organs  of  fenfe  to  the  ftimulus  of  the  eiecftric  fluid  in  fuddenly 
palling  through  them. 

VI.  Of  the  Safe  of  Heat. 

There  are  many  experiments  in  chemical  writers,  that  evince 
the  exiftence  of  heat  as  a fluid  element,  which  covers  and  per- 
vades all  bodies,  and  is  attracted  by  the  folutions  of  fome  of 
them,  and  is  detruded  from  the  combination  of  others.  Thus, 
from  the  combinations  of  metals  with  acids,  and  from  thefe 
combinations  of  animal  fluids,  which  are  termed  fecretions, 
this  fluid  matter  of  heat  is  given  out  amongft  the  neighbour- 
ing bodies  ; and  in  the  folutions  of  falts  in  water,  or  of  water  in 
air,  it  is  abforbed  by  the  bodies  that  furround  them;  whilft,  in 
its  facility  in  paffing  through  metallic  bodies,  and  its  difficulty 
in  pervading  refins  and  glals,  it  refembles  .the  properties  of  the 
define  aura ; and  is  like  that  excited  by  friction,  and  feems 
like  that  to  gravitate  amongft  other  bodies  in  its  uncombined 
ftate,  and  to  find  its  equilibrium. 

There  is  no  circumftance  of  more  confcquence  in  the  ani- 
mal economy,  than  a due  proportion  of  this  fluid  of  heat;  for 
the  digeftion  of  our  nutriment  in  the  ftomach  and  bowels,  and 
the  proper  qualities  of  all  our  fecreted  fluids,  as  they  are  pro- 
duced or  prepared,  partly  by  animal,  and  partly  by  chemical 
proceffes,  depend  much  on  the  quantity  of.  heat,  the  excels  of 
which,  or  its  deficiency,  alike  gives  us  pain,  and  induces  r^-to 
avoid  the  circumftances  that  occalion  them.  And  in  this  the 
perception  of  heat  effentially  differs  from  the  perceptions  of  tire 
fenfe  of  touch,  as  we  receive  pain  from  too  great  preffure  of 
folid  bodies,  but  none  from  the  abfence  of  it.  It  is  hence  pro- 
bable, that  nature  has  provided  us  with  a let  of  nerves  ror  the 
perception  of  this  fluid,  which  anatomilts  have  not  yet  attend- 
ed to. 

There  may  be  fome  difficulty  in  the  proof  of  this  aflertion  : 
if  we  look  at  a hot  lire-,  we  experience  no  pain  of  the  optic 
- 7-  nerve, 


Sect.  XIV.  7-  PRODUCTION  OF  IDEAS.  87 

nerve,  though  the  heat  along  with  the  light  muff  be  concen- 
trated upon  it.  Nor  does  warm  water  or  warm  oil  poured 
into  the  ear  give  pain  to  the  organ  of  hearing ; and  hence,  as 
thefe  organs  of  fenfe  do  not  perceive  fmall  exceffes  or  deficien- 
cies of  heat,  and  as  heat  has  no  greater  analogy  to  the  folidity 
or  to  the  figures  of  bodies,  than  it  has  tp  their  colours  or  vi- 
brations, there  feems  no  fufficient  reafon  for  our  afcribing  the 
perception  of  heat  and  cold  to  the  fenfe  of  touch,  to  which  it 
has  been  generally  attributed,  either  becaufe  its  is  diffufed  be- 
neath the  whole  lkiii  like  the  fenfe  of  touch,  or  owing  to  the 
inaccuaracy  of  our  obfervations,  or  the  defecSi  of  our  lan- 
guages. 

There  is  another  circumftance  which  would  induce  us  to 
believe  that  the  perceptions  of  heat  and  cold  do  not  belong  to 
the  organ  of  touch ; fince  the  teeth,  which  are  the  lead  adapted 
For  the  perceptions  of  folidity  or  figure,  are  the  molt  fenfible  to 
heat  or  cold ; whence  we  are  forewarned  from  fwallowing 
thofe  materials,  whofe  degree  of  coldnefs  or  of  heat  would  in- 
jure our  ftomachs. 

The  following  is  an  extract  from  a letter  of  Dr.  R.  W. 
Darwin,  of  Shrewfbury,  when  he  was  a ftudent  at  Edinburgh. 
“ I made  an  experiment  yefterday  in  ourhofpital,  which  much 
•favours  your  opinion,  that  the  fenfation  of  heat  and  of  touch 
depend  on  different  fets  of  nerves.  A man  who  had  lately  re- 
covered from  a fever,  and  was  Hill  weak,  was  ieized  with  vi- 
olent cramps  in  his  legs  and  feet,  which  were  removed  by  opi- 
ates, except  that  one  of  his  feet  remained  infehfibie.  Mr.  Ew- 
art pricked  him  with  a pin  in  five  or  fix  places,  and  the  pa- 
tient declared  he  did  not  feel  it  in  the  leaft,  nor  was  he  fenfi- 
ble of  a very  (mart  pinch.  I then  held  a red  hot  poker  at 
lome  diftance,  and  brought  it  gradually  nearer,  till  it  came 
within  three  inches,  when  he  afferted  that  he  felt  it  quite  dif- 
tindlly.  I fuppofe  fome  violent  irritation  on  the  nerves  of 
touch  had  earned  the  cramps,  and  had  left  them  paralytic  ; 
while  die  nerves  of  heat,  having  fuffered  no  increafe  of  fti- 
rnuius,  retained  their  irritability.” 

VII.  Of  the  Senfe  of  Extenfion. 

The  organ  of  touch  is  properly  the  fenfe  of  preffure,  but 
the  mufcular  "fibres  themfelves  conftitute  the  organ  of  fenfe, 
ihat  feels  extenfion.  The  fenfe  of  preffure  is  always  attend- 
ed with,  tire  ideas  of  the  figure  and  folidity  of  the  objedf,  nei- 
ther of  which  accompany  cur  perception  of  extenfion.  The 
whole  fet  of  muicles,  whether  they  are  hollow  ones,  as  the 
heart,  arteries,  and  inteftines,'  or  longitudinal  ones  attached  to 

bones, 


83 


PRODUCTION  OF  IDEAS.  Sect.  XIV.  7. 

bones,  contract  themfelves, ' whenever  they  are  flimulatedby 
forcible  elongation ; and  it  is  ohfervable,  that  the  white  muf- 
cles, which  conftitute  the  arterial  fyftem,  feem  to  be  excited 
into  contradlion  from  no  other  kinds  of  ftimulus,  according  to 
the  experiments  of  Haller.  And  hence  the  violent  pain  in 
fome  inflammations,  as  in  the  paronychia,  obtains  immediate 
relief  by  cutting  the  membrane,  that  was  ftretched  by  the  tu- 
mour of  the  fubjacent  parts. 

Hence  the  whole  rnufcular fyftem  maybe  confidered  as  one 
organ  of  fenfe,  and  the  various  attitudes  of  the  body,  as  ideas 
belonging  to  this  organ  ; of  many  of  which  we  are  hourly  con- 
scious, while  manyr  others,  like  the  irritative  ideas  of  the  other 
fenfes,  are  performed  without  our  attention. 

When  the  mufcles  of  the  heart  ceafe  to  adl,  the  refluent 
blood  again  diftends  or  elongates  them;  and  thus  irritated,  they 
contract  as  before.  The  fame  happens  to  the  arterial  fyftem, 
and  I fuppofe  to  the  capillaries,  inteftines,  and  yarious  glands 
of  the  body. 

When  the  quantity  of  urine,  or  of  excrement,  diftends  the 
bladder,  or  redtum,  thofe  parts  contract,  and  exclude  their 
contents,  and  many  other  mufcles,  by  aflbeiation,  adt  along 
with  them ; but  if  thefe  evacuations  are  not  loon  complied  with, 
pain  is  produced  by  a little  further  extenfion  of  the  mufcular 
fibres:  a fimilar  pain  is  caufed  in  the  mufcles,  when  a limb  is 
much  extended  for  the  redudtion  of  diflocated  bones ; and  in 
the  punifhment  of  the  rack,  and  in  the  painful  cramps  of  the 
calf  of  the  leg,  or  of  other  mufcles  ; for  a greater  degree  of  con- 
tradtion  of  a mufcle,  than  the  movement  of  the  two  bones  to 
which  its  ends  are  afExed  will  admit  of,  muft  give  fimilar  pain 
to  that  which  is  produced  bv  extending  it  beyond  its  due  length. 
And  the  pain  from  pundtures  or  inciiions  arifes  from  the  dif- 
tention  of  the  fibres,  as  the  knife  pafles  through  them ; for  it 
nearly  ceafes  as  foon  as  the  divifion  is  completed. 

All  thefe  motions  of  the  mufcles,  that  are  thus  naturally  ex- 
cited by  the  ftimulus  of  diftending  bodies,  are  alfo  liable  to  be 
called  into  ftrong  adtion,  by  their  catenation  with  the  irrita- 
tions or  fenfations  produced  by  the  momentum  of  the  progref- 
live  particles  of  blood  in  the  arteries,  as  in  inflammatory'  fe- 
vers ; or  by  acrid  fubftances  on  other  fenfiblc  organs,  as  in  the 
ftrangury,  or  tenefmus,  or  cholera. 

We  fliall  conclude  this  account  of  the  fenfe  of  extenfion  by 
obferving,  that  the  want  of  its  objedt  is  attended  with  a difa- 
greeable  ienfation,  as  well  as  the  excels  of  it.  In  thofe  hollow 
mufcles  which  have  been  accuftomed  to  it,  this  difagreeable 
fenfation  is  called  faintnefs,  emptinefs,  and  finking ; and,  when 


Sect.  XIV.  8.  PRODUCTION  OF  IDEAS.  89 

itarifes  to  a certain  degree,  is  attended  with  fyncope,  or  a total 
quiefcence  of  all  motions  but  the  internal  irritative  ones,  as 
happens  from  fudden  lofs  of  blood,  or  in  the  operation  of  tap- 
ping in  the  dropfy. 

VIII.  Of  the  Appetites  of  Hunger,  Thirji,  Heat,  Extenfon, 

the  \vant  of  frejh  Air,  animal  Love , and  the  fuck  ling  of 

Children.  , 

Hunger  is  mod  probably  perceived  by  thofe  numerous  rami- 
fications of  nerves  that  are  feen  about  the  upper  opening  of 
the  ftomach  ; and  thirft,  by  the  nerves  about  the  fauces,  and 
the  top  of  the  gula.  The  ideas  of  thefe  fenles  are  few  in  the 
generality  of  mankind,  but  are  more  numerous  in  thofe  who,  by 
difeafe  or  indulgence,  defire  particular  kinds  of  foods  or  liquids. 

A fenfe  of  heat  has  already  been  fpoken  of,  which  may 
with  propriety  be  called  an  appetite,  as  we  painfully  defire  it, 
when  it  is  deficient  in  quantity. 

A fenfe  of  extenfion  may  be  ranked  amongft  thefe  appetites, 
fince  the  deficiency  of  its  object  gives  difagreeable  fenfation : 
when  this  happens  in  the  arterial  fyfiem,  it  is  called  faintnefs,  and 
feems  to  bear  fome  analogy  to  hunger  and  to  cold ; which,  like 
it,  are  attended  with  emptinefs  of  a part  of  the  vafcular  fyfiem. 

The  fenfe  of  want  of  frefli  air  has  not  been  attended  to, 
but  is  as  diftindt  as  the  others,  and  thefirft  perhaps  that  we  ex- 
perience after  our  nativity : from  the  want  of  the  objedt  of 
this  fenfe  many  difeafes  are  produced,  as  the  jail-fever,  plague, 
and  other  epidemic  maladies.  Animal  love  is  another  appe- 
tite, which  occurs  later  in  life ; and  the  females  of  ladtiferous 
animals  have  another  natural  inlet  of  pleafure  or  pain  from  the 
fuckling  their  offspring.  The  want  of  which,  either  owing  to 
the  death  of  their  progeny,  or  to  the  fafhion  of  their  country, 
has  been  fatal  to  many  of  the  fex.  The  males  have  alfo  pec  - 
toral  glands,  which  are  frequently  turgid  with  a thin  milk  at 
their  nativity,  and  are  furnifhed  with  nipples,  which  eredt  on 
titillation  like  thofe  of  the  female ; but  which  feem  now  to  be  of 
no  further  ufe,  owing  perhaps  to  fome  change  which  thefe  ani- 
mals have  undergone  in  the  gradual  progreffion  of  the  forma- 
tion of  the  earth,  and  of  all  that  it  inhabit. 

Thefe  feven  laft  mentioned  fenfes  may  properly  be  termed 
appetites,  as  they  differ  from  thofe  of  touch,  fight,  hearing, 
tafte,  and  fmell,  in  this  refpedt ; that  they  are  affected  with  pain, 
as  well  by  the  defect  of  their  objects,  as  by  the  excefs  of  them, 
which  is  not  fo  in  the  latter.  Thus  cold  and  hunger  give  us 
pain,  as  well  as  an  excefs  of  heat  or  fatiety : but  it  is  not  fo 
with  darknefs  and  filence. 

IX,  Before  we  conclude  this  Section  on  the  organs  of  fenfe, 

we 


9® 


CLASSES  OF  IDEAS. 


Sect.  XV.  i. 


we  mu  ft  obferve,  that,  as  far  as  we  know,  there  are  many  more 
fenfes  than  have  been  here  mentioned,  as  every  gland  feems  to 
be  influenced  to  feparate  from  the  biood,  or  to  abforb  from  the 
cavities  of  the  body,  or  from  the  atmofphere,  its  appropriated 
Laid,  by  the  ftimulus  of  that  fluid  on  the  living  gland;  and  not 
by  mechanical  capillary  abforption,  nor  by  chemical  affinity. 

H ence  it  appears,  that  each  of  thefe  glands  mufthave  a pecu- 
liar organ  to  perceive  thefe  irritations ; but,  as  thefe  irritations 
are  not  lucceeded  by  fenfation,  they  have  not  acquired  the  names 
of  fenfes. 

However,  when  thefe  glands  arc  excited  into  motions  ftrong- 
c-r  than  ufual,  either  by  the  acrimony  of  their  fluids,  or  by  their 
own  irritability  being  much  increafed,  then  the  fenfation  of 
pain  is  produced  in  them  as  in  all  the  other  fenfes  of  the  bodv  ; 
mid  thefe  pains  are  all  of  different  kinds ; and  hence  the  glands 
at  this  time  really  become  each  a different  organ  of  fenfe,  though 
thefe  different  kinds  of  pain  have  received  no  names. 

Thus,  a great  excefs  of  light  does  not  give  die  idea  of  light, 
but  of  pain ; as  in  forcibly  opening  the  eye  when  it  is  much 
inflamed.  The  great  excefs  of'preiTure  or  diftention,  as  w hen 
the  point  of  a pin  is  preffed  upon  our  fkin.  produces  pain, 
(and  when  this  pain  of  the  fenfe  of  touch  is  {lighter,  it  is  term-  , 
cd  itching  or  tickling)  without  any  idea  of  fchdity  or  of  figure : 
an  excels  of  heat  produces  fmarting,  of  cold  another  kind  of 
pain:  it  is  probable  by  this  fenfe  of  heat  the  pain  produced  by 
cauftic  bodies  is  perceived,  and  of  electricity,  as  all  theie  are  flu- 
ids, that  permeate,  diftend,  or  decompofe  the  parts  that  feel  them. 


SECT.  XV. 

OF  THE  CLASSES  OF  IDEAS. 

I.  I.  Ideas  received  hi  tribes.  2.  IVe  combine  them  fur- 
ther, cr  abflrad  from  theje  tribes.  3.  Complex  ideas. 
4.  Compounded  ideas.  5.  Simple  ideas,  modes,  JubJien- 
ccs , relations ; general  ideas.  6.  Ideas  oj  reflexion.  J. 
Aleatory  and  imagination  imp  cr  fell  ly  dejined.  1 acal  pre- 
fence.  Alemorandum-mngs.  II.  I.  Irritative  ideas; 
perception.  2.  Senfitive  ideas  ; imagination.  3.  F dun- 
tar  v ideas ; recollect  ion.  4.  Affoctuted  ideas  ; figgejiion. 
III.  1.  Definitions  of  perception;  memory.  2 . Reef  oil- 
ing, judgment,  doubting,  dfiingm fling,  comparing.  3. 
Invention.  4-  Confcioufncfs.  5-  Identity.  6.  L.apje 
of  time.  7.  I rse-vdil. 

I.  AS  the  conftituen?  elements  of  the  material  world  are 
Oii'v  perceptible  to  our  organs  of  fenie  in  a ftate  of  combine- 


Sect.  XV.  i. 


CLASSES  OF  IDEAS, 


91 

rion ; it  follows,  that  the  ideas  or  fenfual  motions  excited  by 
them,  are  never  received  fingly,  but  ever  with  a greater  or  lefs 
degree  of  combination.  So  the  colours  of  bodies,  or  their  hard- 
neffies,  occur  with  their  fingers : every  fmeli  and  tafte  has  its 
degree  of  pungency,  as  well  as  its  peculiar  flavour : and  each 
note  in  mulic  is  combined  with  the  tone  of  fome  inftrument. 
It  appears  from  hence,  that  we  can  be  fenftble  of  a number  of 
ideas  at  the  fame  time,  fuch  as  the  whitenefs,  hardnefs,  and 
coldnefs  of  a fnow-ball,  and  can  experience,  at  the  fame  time, 
many  irritative  ideas  of  furrounding  bodies,  which  we  do  not 
attend  to,  as  mentioned  in  Sedf.  VII.  3.  2.  But  thofe  ideas 
which  belong  to  the  fame  fenfe,  feem  to  be  more  eafily  com- 
bined into  fynchronous  tribes,  than  thofe  which  were  not  re- 
ceived by  the  fame  fenfe,  as  we  can  more  eafily  think  of  the 
whitenefs  and  figure  of  a lump  of  fugar  at  the  fame  time,  than 
the  whitenefs  and  fweetnefs  of  it. 

2.  As  thefe  ideas,  or  fenfual  motions,  are  thus  excited  with 
greater  or  lefs  degrees  of  combination,  fo  we  have  a power, 
when  we  repeat  them  either  by  our  volition  orfenfation,  to  in- 
creafe  or  diminifh  this  degree  of  combination  ; that  is,  to  form 
compounded  ideas  from  thofe  which  were  more  Ample,  and 
abftrad!  ones  from  thofe  which  were  more  complex,  when 
they  were  firft  excited;  that  is,  we  can  repeat  a part,  or  the 
whole  of  thofe  fenfual  motions  which  did  conftitute  our  ideas 
of  perception ; and  the  repetition  of  which  now  conftitutes  our 
ideas  of  recolledfion,  or  of  imagination. 

3.  Thofe  ideas  which  we  repeat  without  change  of  the 
quantity  of  that  combination,  with  which  w7e  firft  received 
them,  are  called  complex  ideas,  as  when  you  recoiled!  Weft- 
minfter  Abbey,  or  the  planet  Saturn ; but  it  muft  be  obferved, 
that  thefe  complex  ideas,  thus  re-excited  by  volition,  fenfation, 
or  afTociation,  are  feldom  perfed!  copies  of  their  correfpond- 
ent  perceptions,  except  in  our  dreams,  where  other  external  ob- 
jedls  do  not  detradl  our  attention. 

4.  Thofe  ideas  which  are  more  complex  than  the  natural 
objects  that  firft  excited  them,  have  been  called  compounded 
ideas,  as  when  we  think  of  a fphinx  or  griffin. 

5.  And  thofe  that  are  lefs  complex  than  the  correfpondent 
natural  objedts,  have  been  tenned  abftradted  ideas : thus  fweet- 
nefs, and  whitenefs,  and  folidity,  are  received  at  the  fame  time 
from  a lump  of  fugar ; yet  I can  recoiled!  any  of  thefe  qualities 
without  thinking  of  the  others,  that  were  excited  along  with 
them. 

When  ideas  are  fo  far  abftradled  as  in  the  above  example, 
they  have  been  termed  fimple  by  the  writers  of  metaphylics, 

O and 


Classes  of  ideas. 


Sect.  XV,  u 


9* 

and  feetn  indeed  to  be  more  complete  repetitions  of  the  ideas 
or  fenfual  motions,  originally  excited  by  external  objedts. 

Other  claffes  of  thefe  ideas,  where  the  abftraction  has  not 
been  fo  great,  have  been  termed,  by  Mr.  Locke,  modes,  fub- 
ftances,  and  relations  ; but  they  feem  only  to  differ  in  their  de- 
gree of  abftraction  from  the  complex  ideas  that  were  at  firft 
excited ; for  as  theie  complex  or  natural  ideas  are  themfelves  im- 
perfedt  copies  of  their  correfponaent  perceptions ; fo  thefe  ab- 
ftradt  or  general  ideas  are  only  (till  more  imperfedt  copies  of 
the  fame  perceptions.  Thus,  when  I have  feen  an  object  but 
once,  as  a rhinoceros,  my  abflradt  idea  of  this  animal- is  the 
fame  as  my  complex  one.  I may  think  more  or  lefs  diftinctlv  of 
a rhinoceros,  but  it  is  the  very  rhinoceros  that  I faw,  or  fome 
part  or  property  of  him  which  recurs  to  my  mind. 

But  when  any  clafs  of  complex  objedts  becomes  the  fubjedt 
of  converfation,  of  which  I have  feen  many  individuals,  as  a 
caftle  or  an  army,  fome  property  or  circumftance  belonging 
to  it  is  peculiarly  alluded  to ; and  then  I feel  in  my  own  mind 
that  my  abftradc  idea  of  this  complex  objedt  is  only  an  idea  of 
that  part,  property,  or  attitude  of  it,  that  employs  the  prefent 
converfation,  and  varies  with  every  fentence  that  is  fpoken  con- 
cerning it.  So,  if  any  one  fhouid  fay,  “ one  may  lit  upon  a 
horfeiafer  than  on  a camel,”  my  abflradt  idea  of  the  two  ani- 
mals includes  only  an  outline  of  the  level  back  of  the  one,  and 
the  gibbolity  on  the  back  of  the  other.  What  noife  is  that  in 
the  ftreet  ? Some  horfes  trotting  over  the  pavement.  Here 
my  idea  of  the  horfes  includes  principally  the  fhape  and  mo- 
tion of  their  legs.  So  alfo  the  abflradt  ideas  of  goodnefs  and 
courage  are  ftill  more  imperfedt  reprefentations  of  the  objedts 
they  were  received  from ; for  here  we  abflradt  the  material  parts, 
and  recolledt  only  the  qualities. 

Thus,  w'e  abflradt  fo  much  from  fome  of  our  complex  ideas, 
that  at  length  it  becomes  difficult  to  determine  of  what  percep- 
tion they  partake ; and  in  many  inflances  our  idea  feems  to  be 
no  other  than  of  the  found  or  letters  of  the  word,  that  Hands 
for  the  colledtive  tribe,  of  which  we  are  faid  to  have  an  ab- 
flradted  idea,  as  noun,  verb,  chimera,  apparition. 

6.  Ideas  have  been  divided  into  thofe  of  perception,  and  thofe 
of  refiedtion  ; but  as  whatever  is  perceived  mull  be  external 
to  the  organ  that  perceives  it,  all  our  ideas  mull  originally  be 
ideas  of  perception. 

7.  Others  have  divided  our  ideas  into  thofe  ot  memory,  and 
thefe  of  imagination ; they  have  faid  that  a recollection  of  ideas, 
in  the  order  they  were  received,  conftitutes  memory,  and  with- 
out that  order,  imagination ; but  all  die  ideas  of  unagination, 

except 


Sect.  XV.  2. 


CLASSES  OF  IDEAS. 


-93 

except  the  few  that  are  termed  fimple  ideas,  are  parts  of  trains 
or  tribes  in  the  order  they  were  received;  as,  if  I think  of  a 
fphinx,  or  a griffin,  the  fair  face,  bofom,  wings,  claws,  tail, 
are  all  complex  ideas  in  the  order  they  were  received;  and  it 
behoves  the  writers,  who  adhere  to  this  definition,  to  determine 
how  fmall  the  trains  muft  be,  that  fhall  be  called  imagination, 
and  how  great  thofe  which  fhall  becalled  memory. 

Others  have  thought  that  the  ideas  of  memory  have  a greater 
vivacity  than  thofe  of  imagination  ; but  the  ideas  of  a perfon  in 
fleep,  or  in  a waking  reverie,  where  the  trains  connedied  with 
fenfation  are  uninterrupted,  are  more  vivid  and  diftindt  than 
thofe  of  memory,  fo  that  they  cannot  be  diftinguifhed  by  this 
criterion. 

The  very  ingenious  author  of  the  Elements  of  Criticifm 
has  defcribed  what  he  conceives  to  be  a fpecies  - of  memory, 
and  calls  it  ideal  prefence;  but  fire  inftances  he  produces  are 
the  reveries  of  fenfation,  and  are,  therefore,  in  truth,  connec- 
tions of  the  imagination,  though  they  are  recalled  in  the  order 
they  were  received. 

The  ideas  connected  by  afTociafion  are,  in  common  dif- 
courfe,  attributed  to  memory,  as  we  talk  of  memorandum- 
rings,  and  tie  a knot  on  our  handkerchiefs  to  bring  fomething 
Into  our  minds  at  a diftance  of  time.  And  a fchool-boy,  who 
can  repeat  a thoufand  unmeaning  lines  in  Lilly’s  Grammar,  is 
faid  to  have  a good  memory.  But  thefe  have  been  already 
fhewn  to  belong  to  the  clafs  of  affociatian,  and  are  termed 
ideas  of  fuggeition. 

II.  Laftly,  the  method  already  explained,  of  claffing  ideas 
into  thofe  excited  by  irritation,  fenfation,  volition,  or  affocia- 
tron,  we  hope  will  be  found  more  convenient,  both  for  explain- 
ing the  operations  of  the  mind,  and  for  comparing  them  with 
thofe  of  the  body ; and  for  the  illuftration  and  the  cure  of  the 
difeafes  of  both,  and  which  we  fhall  here  recapitulate. 

1.  Irritative  ideas  are  thofe  which  are  preceded  by  irrita- 

tion, which  is  excited  by  objeriis  external  to  the  organs  of  fenfe  : 
as  the  idea  of  that  tree,  which  either  I attend  to,  or  which  I 
fhun  in  walking  near  it  without  attention.  In  the  former  cafe, 
it  is  termed  perception,  in  the  latter,  it  is  termed  limply  an  ir- 
ritative idea.  * - 

2.  Senfitive  ideas  are  thofe  which  are  preceded  by  the  fen- 
fation of  pleafure  or  pain,  as  the  ideas  which  conftitute  our 
dreams  or  reveries : this  is  called  imagination. 

3.  Voluntary  ideas  are  thofe  w'hich  are  preceded  by  volun- 
tary exertion,  as  when  I repeat  the  alphabet  backwards : this  is 
called  recolledtion. 


4.  AfTociaty 


CLASSES  OF  IDEAS. 


94 


Sect. XV.  3. 


4.  AITociate  ideas  are  thofe  which  are  preceded  by  other 
ideas,  or  mufcular  motions,  as  when  we  think  over  or  repeat 
the  alphabet  by  rote  in  its  ufual  order,  or  fing  a tone  we  are 
accuftomed  to : this  is  called  fuggeftion. 

IIL  1.  Perceptions  fignify  thofe  ideas  which  are  preceded 
by  irritation,  and  fucceeded  by  the  fenfation  of  pleafure  or  pain ; 
for  whatever  excites  our  attention  interefls  us ; that  is,  it  is 
accompanied  with  pleafure  or  pain,  however  flight  may  be  the 
degree  or  quantity  of  either  of  them. 

The  word  memory  includes  two  clafles  of  ideas,  either  thofe 
which  are  preceded  by  voluntary  exertion,  or  thofe  which  are 
fuggefted  by  their  aflbciations  with  other  ideas. 

2.  Reafoning  is  that  operation  of  the  fenforium  by  which 
we  excite  two  or  more  tribes  of  ideas,  and  then  re-excite  the 
ideas  in  which  they  differ,  or  correfpond.  If  we  determine 
this  difference,  it  is  called  judgment ; if  we  in  vain  endeavour 
to  determine  it,  it  is  called  doubting. 

If  we  re-excite  the  ideas  in  which  they  differ,  it  is  called 
diftinguilhing.  If  we  re-excite  thofe  in  which  they  correfpond, 
it  is  called  comparing. 

3.  Invention  is  an  operation  of  the  fenforium,  by  which 
we  voluntarily  continue  to  excite  one  train  of  ideas  ; fuppofe 
the  deflgn  of  raifing  water  by  a machine  ; and  at  the  fame  time 
attend  to  all  other  ideas  which  are  connected  with  this  by  eve- 
ry kind  of  catenation,  and  combine  or  feparate  them  volunta- 
rily for  the  purpofe  of  obtaining  fome  end. 

For  we  can  create  nothing  new,  we  can  only  combine  or  fe- 
parate tiie  ideas  which  we  have  already  received  by  our  per- 
ceptions: thus,  if  I wifh  to  reprefent  a monfter,  I call  to  my 
mind  the  ideas  of  every  thing  difagreeable  and  horrible,  and 
combine  the  na^linefs  and  gluttony  of  a hog,  the  ftupidity  and 
obftinacy  of  an  afs,  with  the  fur  and  awkwardnefs  of  a bear,  and 
call  the  new7  combination  Caliban.  Yet  fuch  a monfter  may 
exift  in  nature,  as  all  his  attributes  are  parts  of  nature.  So, 
when  I wifii  to  reprefent  every  thing  that  is  excellent  and  ami- 
able; when  I combine  benevolence  with  cheerfulneis,  wifdom, 
knowledge,  tafte,  wit,  beauty  of  perfon,  and  elegance  of  man- 
ners, and  affociate  them  in  one  lady,  as  a pattern  to  the  w7orld, 
it  is  called  invention ; yet  fuch  a perfon  may  exift, — fuch  a 
perfon  does  exift  ! — It  is , who  is  as  much  a mon- 

fter as  Caliban. 

4.  In  relpedt.  to  ccnfcioufnefs,  we  are  only  confcious  of 
our  exiftence  when  we  think  about  it;  as  we  only  perceive 
the  lapfe  of  time  when  wTe  attend  to  it ; when  we  are  bulled 
about  other  objects,  neither  the  lapfe  of  the  time,  nor  thecon- 

fcioufnef* 


CLASSES  OF  IDEAS. 


Sect.  XV.  3. 


95 


fcioufnefs  of  our  own  exiftence,  can  occupy  our  attention. 
Hence,  when  we  think  of  our  own  exiftence,  we  only  excite 
abftradted  or  reflex  ideas  (as  they  are  termed)  of  our  principal 
pleafures  or  pains,  of  our  defires  or  avarfions,  or  of  the  figure, 
folidity,  colour,  or  other  properties  of  our  bodies,  and  call  that 
act  of  the  fenforium  a confcioufnefs  of  our  exiftence.  Some 
philofopher,  I believe  it  is  Des  Cartes,  has  laid,  “ I think, 
therefore  I exift.”  But  this  is  not  right  reafoning,  becaufe 
thinking  is  a mode  of  exiftence;  and  it  is  thence  only  faying, 
“ I exift,  therefore  I exift.”  For  there  are  three  modes  of 
exiftence,  or  in  the  language  of  grammarians,  three  kinds  of 
verbs.  Firft,  fimply,  I am,  or  exift.  Secondly,  I am  acting, 
or  exift  in  a flate  of  activity,  as  I move.  Thirdly,  I am  fuf- 
fering,  or  exift  in  a ftate  of  being  adted  upon,  as  I am  moved. 
The  when,  and  the  where,  as  applicable  to  this  exiftence,  de- 
pends on  the  lucceffive  motions  of  our  own  or  of  other  bodies, 
and  on  their  refpedtive  fttuations,  asfpoken  of,  Se6t.  XIV.  2. 5. 

5.  Our  identity  is  known  by  our  acquired  habits,  or  catenat- 
ed trains  of  ideas  and  mufcular  motions ; and,  perhaps,  when 
we  compare  infancy  with  old  age,  infthofe  alone  can  our  iden- 
tity be  fuppofed  to  exift.  For  what  elfe  is  there  of  fimilitude 
between  the  firft  fpeck  of  living  entity  and  the  mature  man  ? 
Every  dedudfion  of  reafoning,  every  fentiment  or  paflion,  with 
every  fibre  of  the  corporeal  part  of  our  fyftem,  has  been  fub- 
jedf  almoft  to  annual  mutation  ; while  fome  catenations  alone 
of  our  ideas  and  mufcular  adtions,  have  continued  in  part  un- 
changed. 

By  the  facility  with  which  we  can,  in  our  waking  hours, 
voluntarily  produce  certain  fucceffive  trains  of  ideas,  we  know 
by  experience,  that  we  have  before  re-produced  them  ; that  is, 
we  are  confcious  of  a time  of  our  exiftence,  previous  to  the 
prefent  time  ; that  is,  of  our  identity  now  and  heretofore.  It  is 
thefe  habits  of  adtion,  thefe  catenations  of  ideas  and  mufcular 
motion,  which  begin  with  life,  and  only  terminate  with  it;  and 
which  we  can  in  fome  meafure  deliver  to  our  pofterity,  as  ex- 
plained in  Sea.  XXXIX. 

6.  When  the  progreffive  motions  of  external  bodies  make  a 
part  of  our  prelent  catenation  of  ideas,  we  attend  to  the  lapfe 
of  time,  which  appears  the  longer  the  more  frequently  we 
thus  attend  to  it ; as  when  we  expea  fomething  at  a certain 
how,  which  much  interefts  us,  whether  it  be  an  agreeable  or 
difagreeable  event,  or  when  we  count  the  palling  feconds  on  a 
ftop-watch, 

- When  an  idea  of  our  own  perfon,  or  a reflex  idea  of  our 
pleafures  and  pains,  defires  and  averfions,  makes  a part  of  this 

catenation, 


OF  INSTINCT. 


Sect.  XVI. 


.96 

catenation,  it  is  termed  confcioufnefs  ; and  if  this  idea  of  con- 
'feioufnefs  make  a part  of  a catenation,  which  wc  excite  by 
recolledtion.  and  know  by  the  facility  with  which  we  excite  it, 
that  we  have  before  experienced  it,  it  is  called  identity,  as  ex- 
plained above. 

7.  In  refpedl  to  free-will,  it  is  certain,  that  we  cannot  will 
to  think  of  a jiew  train  of  ideas,  without  previoufly  thinking 
of  the  hrft  link  of  it;  as  I cannot  will  to  think  of  a black  fwan 
without  previoufly  thinking  of  a .black  fwan.  But,  if  I 
now  think  of  a tail,  I can  voluntarily  recollect  ail  animals 
which  have  tails;  my  will  is  fo  tar  free,  that  lean  purfue  the 
ideas  linked  to  this  idea  at  tail,  as  far  as  my  knowledge  of  the 
fubjedt  extends ; but  to  will  without  motive  is  to  will  without 
deGre  or  averfion,  which  is  as  abfurd  as  to  feel  without  plea- 
sure or  pain  ; they  are  both  foiefcifms  in  the  terms.  So  far  are 
we  governed  by  the  catenations  of  motions,  which  affect  both 
the  body  and  the  mind  of  man,  and  which  begin  with  our  ir- 
ritability, and  end  with  it. 


SECT.  XVI. 

OF  INSTINCT. 

Haud  equidem  credo,  quia  sitdivinitus  illis 
Ingeuium,  aut  rerum  fato  prudentia  major. 

Virg.  Georg.  L.  I.  41 5. 

I.  Inf  in  Clive  anions  defined.  Of  connate  pajfons.  II. 
Of  the  fenfations  and  motions  of  the  foetus  in  the  womb. 
ill.  Some  animals  are  more  perfectly  formed  than  others 
before  nativity.  Of  learning  to  walk.  IV.  Of  the /wal- 
lowing, breathing , fucking,  pecking,  and  lapping  of  young 
animals.  V.  Of  the  fenfe  of  [me If  and  its  ufes  to  ani- 
mals. Why  cats  do  not  eat  their  kittens.  W.  Of  the 
accuracy  of  fght  in  mankind , and  their  fenfe  of  beauty. 
Of  the  fenfe  of  touch  in  elephants , monkies , beavers , men. 
VII.  Of  natural  language.  VIII.  The  origin  of  natural 
language:  1.  The  language  of  fear  ; 2.  of  grief ; 3.  of 
tender  pie  a fur  c ; 4.  of  ferene  pleafurc ; 5.  of  anger  ; 6. 
cf  attention.  IX.  Artificial  language  of  turkies,  hens, 
ducklings , wagtails,  cuckoos,  rabbits,  dogs  and  nightin- 
gales. X.  Of  mufc\  of  tooth-edge ; of  a good  ear;  of 
architecture.  XI.  Of  acquired  knowledge ; of  foxes, 
rooks,  fieldfares , lapwings,  dogs,  cats,  horfes,  crows  and 
pelicans.  XII.  Of  birds  of  paffage,  dormice,  fnakes,  bats, 
j wallows , quails,,  ringdoves,  fare,  chaffinch , hoopoe,  chat- 
terer. 


Sect.  XVI.  i. 


OF  INSTINCT. 


97 

terer,  hem  finch,  erofsbill,  rails , and  cranes.  XIII.  Of 
birds’  nefls  ; of  the  cuckoo  ; of  f wallows’  nefs  ; of  the  /m- 
lor  bird.  XIV.  0/~  t/ze  o/<J  foldier  ; 0/  haddocks , cods,, 
and  dog-fij/r,  of  the  remora  ; of  crabs,  herrings , and  fal~ 
mon.  XV.  0/" fpiders , caterpillars , n;z/r,  mz<Z  tfe  A/;- 
neumon.  XVI.  I.  0/"  locufs •,  gnats-,.  2.  ; 3.  dor- 

mice,fics , worms,  ants,  and  ivafps.  XVII.  0/  the  fa- 
culty that  dijlinguijhes  man  from  the  brutes. 

I.  ALL  thofe  internal  motions  of  animal  bodies  which 
contribute  to  digeft  their  aliment,  produce  their-  fecretions,  re- 
pair their  injuries,  or  increafe  their  growth,  are  performed 
without  our  attention  or  confcioufnels.  They  exift  as  well 
in  our  fleep  as  in  our  waking  hours,  as  wrell  in  the  fetus  dur- 
ing the  time  of  geftation,  as  in  the  infant  after  nativity,  and 
proceed  with  equal  regularity  in  the  vegetable  as  in  the  ani- 
mal fyffem.  Thefe  motions  have  been  fhewn,  in  a former  part, 
of  this  work,  to  depend  on  the  irritations  of  peculiar  fluids,  and 
as  they  have  never  been  ciaffed  amongft  the  inftinclive  actions 
of  animals,  are  precluded  from  our  prefent  difquifition. 

But  all  thofe  actions  of  men  or  animals  that  are  attended 
with  confeioufnefs,  and  feem  neither  to  have  been  directed  by 
their  appetites,  taught  by  their  experience,  nor  deduced  from 
obfervation  or  tradition,  have  been  referred  to  the  power  of  in- 
ftindl.  And  this  power  has  been  explained  to  be  a divine 
fomething,  a kind  of  infpiration,  whilft  the  poor  animal  that 
pofTefTes  it,  has  been  thought  little  better  than  a machine. 

The  irkfomenefs  that  attends  a continued  attitude  of  the 
body,  or  the  pains  that  we  receive  from  heat,  cold,  hunger,  or 
other  injurious  circumftances,  excite  us  to general  locomotion  : 
and  our  lenfes  are  fo  formed  and  eonffftuted  bv  the  hand  of  na- 
ture, that  certain  objects  prefent  us  with  pleafure,  others  with 
pain;  and  we  are  induced  to  approach  and  embrace  thefe,  to 
avoid  and  abhor  thofe,  as  fuch  fenfations  diredt  us. 

Thus,  the  palates  of  fome  animals  are  gratefully  affected  by 
the  maftication  of  fruits,  others  of  grains,  and  others  of  flefh ; 
and  they  are  thence  inftigated  to  attain,  and  to  confume  thofe 
materials,  and  are  furnifhed  with  powers  of  mufcular  motion, 
and  of  digeftion  proper  for  fuch  purpofes. 

Thefe  fenfations  and  defres  conftitutea  part  of  our  fyftem, 
as  our  mufcles  and  bones  conftitute  another  part:  and  hence 
they  may  alike  be  termed  natural  or  connate ; but  neither  of 
them  can  properly  be  termed  infinitive  : as  the  word  inftindt, 
in  its  ufual  acceptation,  refers  only  to  the  adiions  of  animals, 
as  above  explained : the  origin  of  thefe  allions  is  the  fubjedt 
of  our  prefeat  enquiry. 


The 


OF  INSTINCT. 


Sect.  XVI.  z 


98 

The  reader  is  intreated  carefully  to  attend  to  this  definition 
of  infllndiive  actions,  left,  by  ufing  the  word  inftindt  without 
adjoining  any  accurate  idea  to  it,  he  may  not  only  include  the 
natural  defires  of  love  and  hunger,  and  the  natural  fenfations 
of  pain  or  pleafure,  but  the  figure  and  contexture  of  the  body, 
and  the  faculty  of  reafon  itfelf  under  this  general  term. 

II.  We  experience  fome  fenfations,  and  perform  fome  ac- 
tions before  our  nativity;  the  fenfations  of  cold  and  warmth, 
agitation  and  reft,  fulnefs  and  inanition,  are  inftances  of  the 
former;  and  the  repeated  ftruggles  of  the  limbs  of  the  foetus, 
which  begin  about  the  middle  of  geftation,  and  thofe  motions 
by  which  it  frequently  wraps  the  umbilical  chord  around  its 
neck  or  body,  and  even  fometimes  ties  it  on  a knot,  are  inftances 
of  the  latter.  Smellie’s  Midwifery,  vol.  I.  p.  192. 

By  a due  attention  to  thefe  circumftances,  many  of  the  ac- 
tions of  young  animals,  which  at  firft  fight  fieemed  only  refer- 
able to  an  inexplicable  inftincf,  will  appear  to  have  been  ac- 
quired like  ail  other  animal  adfions,  that  are  attended  with  con- 
icioufneis,  by  the  repeated  efforts  of  our  mufcles  under  the 
conduct  of  our  fenfations  or  defires. 

The  chick  in  the  fhell  begins  to  move  its  feet  and  legs  on 
the  fixth  day  of  incubation  (Mattreiean,  p.  1 3 1 ) ; or  on  the 
feventh.day  (Langley);  afterwards  they  are  fieen  to  move 
themfelves  gently  in  the  liquid  that  lurrounds  them,  and  to  open 
and  Ihut  their  mouths,  (Hervei  de  Generat.  p.  62,  and  197. 
Form  de  Poulet.  ii.  p.  129).  Puppies,  before  the  membranes 
are  broken  that  involve  them,  are  leen  to  move  themfelves.  to 
put  out  their  tongues,  and  to  open  and  fhut  their  mouths, 
(Hervey,  Gipfon, Riolan,  Haller).  And  calves  lick  themfelves, 
and  fwallow  many  of  their  hairs  before  their  nativity  : which, 
however,  puppies  do  not,  (Swammerden,  p.  319.  Flemyng 
Phil.  Tranf.  Ann.  1*755.  42)-  And  towards  the  end  of  gef- 
tation, the  fcetus  of  all  animals  are  proved  to  drink  pare  of 
the  liquid  in  which  they  fwim,  (Haller.  Phyfiol.  T.  b.  204). 
The  white  of  egg  is  found  in  the  mouth  and  gizzard  of  the 
chick,  and  is  nearly  or  quite  confirmed  before  it  is  hatched, 
(Harvei  de  Generat.  58).  And  the  liquor  amnii  is  found  in 
the  mouth  and  ftomach  of  the  human  foetus,  and  of  calves ; 
and  how  elie  fhould  that  excrement  be  produced  in  the  intel- 
tines  of  all  animals,  which  is  voided  in  great  quantity  loon  af- 
ter their  birth?  (Gipfon.  Med.  EfFays,  Edinb.  V.  i.  13.  Hulle- 
ri  Phyfiolog.  T.  3.  p.  318.  and  T.  8).  In  the  ftomach  ol  a 
calf,  the  quantity  of  this  liquid  amounted  to  about  three  pints, 
and  the  hairs  amongftit  were  of  the  fame  colour  with  thole  on 
its  fkin,  (Blairi  Anat.  Animal,  p.  in.  122).  Thefe  fadfs  are 

attefted 


OF  INSTINCT. 


DECT.  XVI.  3,4. 


99 


attefted  by  many  other  writers  of  credit  befides  thofe  above 
mentioned. 

III.  It  has  been  deemed  a furprifmg  inftance  of  inftincft, 
that  calves  and  chickens  fhould  be  able  to  walk  by  a few  ef- 
forts, almofl  immediately  after  their  nativity ; whilft  the  human 
infant,  in  thofe  countries  where  he  is  not  incumbered  with 
clothes,  as  in  India,  is  five  or  fix  months,  and  in  our  climate  al- 
moft  a twelvemonth,  before  he  can  fafely  Hand  upon  his  feet. 

The  flruggles  of  all  animals  in  the  womb  mull  referable 
their  mode  of  fwimming,  as  by  this  kind  of  motion  they  can 
beft  change  their  attitude  in  water.  But  the  fwimming  of  the 
calf  and  chicken  refembles  their  manner  of  walking,  which  they 
have  thus,  in  part,  acquired  before  their  nativity,  and  hence 
accomplilh  it  afterwards  with  very  few  efforts ; whilft  the 
fwimming  of  the  human  creature  refembles  that  of  the  frog,  and 
totally  differs  from  his  mode  of  walking. 

There  is  another  circumftance  to  be  attended  to  in  this  affair, 
that  not  only  the  growth  of  thofe  peculiar  parts'  of  animals 
which  are  ftrft  wanted  to  fecure  their  fubfiftence,  are,  in  general, 
furtheft  advanced  before  their  nativity ; but  fome, animals  come 
into  the  world  more  completely  formed  throughout  their  whole 
fyftem  than  others,  and  are  thence  much  forwarder  in  all  their 
habits  of  motion.  Thus  the  colt  and  the  lamb  are  much  more 
perfect  animals  than  the  blind  puppy  and  the  naked  rabbit ; and 
the  chick  of  the  pheafant  and  the  partridge  has  more  perfefit 
plumage  and  more  perfedl  eyes,  as  well  as  greater  aptitude  to 
locomotion,  than  the  callow  neftlings  of  the  dove  and  of  the 
wren.  The  parents  of  the  former  only  find  it  neceffary  to  fhew 
them  their  food,  and  to  teach  them  to  take  it  up ; whilft  thofe 
of  the  latter  are  obliged,  for  many  days,  to  obtrude  it  into  their 
gaping  mouths. 

IV.  From  the  facts  mentioned  in  No  2.  of  this  fcction,  it  is 
evinced,  that  the  foetus  learns  to  fwaliow  before  its  nativity ; for 
it  is  feen  to  open  its  mouth,  and  its  ftomach  is  found  filled  with 
the  liquid  that  furrounds  it.  It  opens  its  mouth,  either  infti- 
gated  by  hunger,  or  by  the  irkfomenefs  of  a continued  attitude 
of  the  mufcles  of  its  face  ; the  liquor  amnii,  in  which  it  fwims, 
is  agreeable  to  its  palate,  as  it  eonfifts  of  a nouriftiing  material. 
(Haller  Phyf.  T.  8.  p.  204).  It  is  tempted  to  experience  its  tafte 
further  in  the  mouth,  and  by  a few  efforts  learns  to  fwaliow, 
in  the  fame  manner  as  we  learn  all  other  animal  a£tions,  which 
are  attended  with  confcioufnefs,  by  the  repeated  efforts  of  our 
mufcles  under  the  condutl  of  our  fcnfatlons  or  volitions. 

The  infpiration  of  air  into  the  lungs  is  fo  totally  different 
from  that  of  fwallowing  a fluid  in  which  we  are  immerfed, 

P that 


OF  INSTINCT. 


Joo 


Sect.  XVI.  4. 


that  it  cannot  be  acquired  before  our  nativity.  But  at  fhis- 
tirne,  when  the  circulation  of  the  blood  is  no  longer  continued 
through  the  placenta,  that  fuffocating  fenfation  which  we  feel 
about  the  prsecordia  when  we  are  in  want  of  frefh  air,  difagree- 
ably  affedts  the  infant : and  all  the  mufcels  of  the  body  are  ex- 
cited into  action  to  relieve  this  oppreflion:  thofe  of  the  breafl, 
ribs,  and  diaphragm  are  found  to  anfwer  this  purpofe  ; and  thus 
refpiration  is  difcovered,  and  is  continued  throughout  our  lives, 
as  often  as  the  oppre.Tion  begins  to  recur.  Many  infants,  both 
of  the  human  creature  and  of  quadrupeds,  Uruggle  for  a mi- 
nute after  they  are  born  before  they  begin  to  breathe,  (Haller 
Phyf.T.  8.  p.  400.  ib.  pt.  2.  p.  1) . Mr.  Buffon  thinks  the  adticn 
of  the  dry  air  upon  the  nerves  of  fine!!  of  new-born  animals, 
by  producing  an  endeavour  to  fneeze,  mav  contribute  to  in- 
duce this  firfc  infpiration  ; and  that  the  rarefadfion  of  the  air, 
by  the  warmth  of  the  lungs,  contributes  to  induce  expiration, 
(Hift.  Nat,  Tom.  4.  p.  174.)  Which  latter  it  may  effect  by 
producing  a difagreeable  fenlation  by  its  delav,  and  a confequent 
effort  to  relieve  it.  Many  children  ineeze  before  they  relpire, 
but  not  all,  as  far  as  I have  obferved,  or  can  learn  from  others. 

At  length,  by  the  diredfion  of  its  fenfe  of  fmell,  or  by  the 
officious  care  of  its  mother,  the  young  animal  approaches  the 
odoriferous  rill  of  its  future  nourifhment,  already  experienced 
to  fwallow.  But  in  the  adt  of  fwallowing,  it  is  neceffary  nearly 
to  clofe  the  mouth,  whether  tire  creature  be  immerfed  in  the  fluid 
it  is  about  to  drink  or  not:  hence,  when  the  child  tirft  attempts 
to  fuck,  it  does  not  flightly  comprefs  the  nipple  between  its  lips, 
and  fuck  as  an  adult  perfon  would  do,  by  abforbing  the  milk; 
but  it  takes  the  whole  nipple  into  its  mouth  for  this  purpofe, 
compreffes  it  between  its  gums,  and  thus  repeatedly  chewing  (as 
it  were)  the  nipple,  preffes  out  the  milk;  exadtly  in  the  tame 
manner  as  it  is  drawn  from  the  teats  of  cows  bv  the  hands  of  the 
milkmaid.  The  celebrated  Hervey  obferves,  that  the  foetus  in 
the  womb  muff  have  fucked  in  a part  of  its  nourifhment,  be- 
caufe  it  knows  how  to  fuck  the  minute  it  is  born,  as  any  one 
may  experience  bv  putting  a finger  between  its  lips,  and  becaufe 
in  a few  days  it  forgets  this  art  of  fucking,  and  cannot  without 
fome  difficulty  again  acquire  it,  (Exercit.  de  Gener.-Anim.  4S. ) 
The  fame  obfervation  is  made  by  Hippocrates. 

A little  further  experience  teaches  the  young  animal  to  fuck 
by  abforption,  as  well  as  by  compreflion ; that  is,  to  open  the 
cheftas  in  the  beginning  of  refpiration,  and  thus  to  rarefy  the 
air  in  the  mouth,  that  the  preffure  of  the  denfer  external  at- 
mofphere  may  contribute  to  force  out  the  milk. 

The  chick  vet  in  the  fhell  has  learnt  to  to  drink  bv  fwallow- 


OF  INSTINCT. 


tot 


Sect.  XVI.  5. 

ing  a part  of  the  white  of  the  egg  for  its  food ; but  not  having 
experienced  how  to  take  up  and  1 wallow  folid  feeds,  or  grains, 
is  either  taught  by  the  folicitops  induftry  of  its  mother ; or  by 
many  repeated  attempts  is  enabled  at  length  to  diftinguifh  and 
to  fw  allow  this  kind  of  nutriment. 

And  puppies,  though  they  knowhow  to  fuck  like  other  ani- 
mals, from  their  previous  experience  in  fwaliowing,  and  in  re- 
spiration, yet  are  they  long  in  acquiring  the  art  ol  lapping  with 
their  tongues,  which,  from  the  flaccidity  of  their  cheeks  and 
length  of  their  mouths,  is  afterwards  a more  convenient  way 
■for  them  to  take  in  water. 

V.  The  fenfes  of  fmell  and  tafle  in  many  other  animals 
greatly  excell  thofe  of  mankind  ; for  in  civilized  fociety,  as  our 
victuals  are  generally  prepared  by  others,  and  are  adulterated 
with  fait,  fpice,  oil,  and  empyreuma,  we  do  not  hefitate  about 
■eating  whatever  is  fet  before  us,  and  neglect  to  cultivate  thefe 
fenfes  ; whereas  other  animals  try  every  morfel  by  the  fmell  be- 
fore they  take  it  into  their  mouths,  and  by  the  taite  before  they 
fwallow  it:  and  are  led  not  only  each  to  his  proper  nourifh- 
menf  by  this  organ  of  fenfe,  but  it  alfo,  at  a maturer  age,  di- 
rects them  in  the  gratification  of  their  appetite  of  love.  Which 
may  be  further  underflood  by  confidering  the  fympathles  of 
thefe  parts  defcribed  in  Clals  IV.  2.  X.  7.  While  the  human 
animal  is  diretfted  to  the  obje£l  of  his  love  by  his  fepfe  of  beau  , 
ty^,  as  mentioned  in  No.  VI.  of  this  Sedfion.  Thus,  Virgil, 
Georg.  III.  250. 

Nonne  vides,  ut  tota  tremor  pertentet  equomm 
Corpora,  si  tantum  notas  odor  attulit  auras? 

Nonne  cams  nidum  veneris  nasutus  odore 
Quaerit,  et  erranti  trahitur  sublambere  lingua? 

Respuit  at  gustum  cupidus,  labiisque  retradfis 
Elevat  os,  trepidansque  novis  percutitur  $stris, 

Inserit  et  vivum  feiici  vomere  semen.— ^ 

Quam  tenui  filo  cascos  adnedfit  amores 
Dodla  Venus,  vitasque  monet  renovare  favillam! 

Anon. 

The  following  curious  experiment  is  related  by  Galen.— 
“ On  differing  a goat  great  with  young,  I found  a brifk  em- 
bryon,  and  having  detached  it  from  the  matrix,  and  fnatching 
it  away  before  it  law  its  dam,  I brought  irinto  a certain  room, 
where  there  were  many  veflels,  fome  filled  with  wine,  ethers 
with  oil,  fome  with  honey,  others  with  milk,  or  fome  other 
liquor ; and  in  others  were  grains  and  fruits : we  hrfl  obferved 
the  young  animal  get  upon  its  feet  and  walk ; then  it  fhook  it- 
felf,  and  afterwards  fcratched  its  fide  with  one  of  its  feet : then 

we 


IC2 


OF  INSTINCT. 


Sect.  XVI.  6. 


we  law  it  fuelling  to  every  one  of  thefe  things  that  were  let 
in  the  room;  and  when  it  had  hnelt  to  them  all,  it  drank  up  the 
milk.”  L.  6.  de  locis.  cap.  6. 

Parturient  quadrupeds,  as  cats,  and  bitches,  and  lows,  are  led 
by  their  fenfe  of  fmell  to  eat  the  pleacenta  as  other  common 
food;  why  then  do  they  not  devour  their  whole  progeny,  as  is 
reprefented  in  an  ancient  emblem  of  Time  ? This  is  laid  fome- 
times  to  happen  in  the  unnatural  ftate  in  which  we  confine 
fows  ; and  indeed  nature  would  feem  to  have  endangered  her 
offspring  in  this  nice  circumftance ! But  at  this  time  the  ftirnu- 
lus  of  the  milk  in  the  tumid  teats  of  the  mother  excites  her  to 
look  out  for,  and  to  defire  fome  unknown  circumftance  to  re- 
lieve her.  At  the  fame  time  the  fmell  of  the  milk  attracts  the 
exertions  of  the  young  animals  towards  its  fource,  and  thus  the 
delighted  mother  dileovers  a new  appetite,  as  mendoned  in  Se£f. 
XIV.  8.  and  her  little  progeny  are  led  to  receive  and  to  com- 
municate pleaiure  by  this  moft  beautiful  contrivance. 

VI.  But  though  the  human  fpecies  in  fome  of  their  fenfa- 
tions  ar  e much  inferior  to  other  animals,  yet  the  accuracy  of 
the  fenfe  of  touch,  which  they  poflefs  in  fo  eminent  a degree, 
gives  them  a great  fuperiority  of  underftanding;  as  is  well  ob- 
ferved  by  the  ingenious  Mr.  ButFon.  The  extremities  of  other 
animals  terminate  in  horns,  and  hoofs,  and  claws,  very  unfit  for 
the  fenfation  of  touch ; whilft  the  human  hand  is  finely  adapted 
to  encompafs  its  object  with  this  organ  of  fenfe. 

The  elephant  is  indeed  endued  with  a fine  fenfe  of  feeling  at 
the  extremity  of  his  probofcis,  and  hence  has  acquired  much 
more  accurate  ideas  of  touch  and  of  fight  than  moft  other  crea- 
tures. The  two  following  inftances  of  the  fagacity  of  thefe 
animals  may  entertain  the  reader,  as  they  were  told  me  bv  fome 
gentlemen  of  diftinct  obfervation,  and  undoubted  veracity,  who 
had  been  much  converfant  with  our  eaftern  fettlcments.  Firft, 
the  elephants  that  are  ufed  to  carry  the  baggage  ot  our  armies, 
are  put  each  under  the  care  of  one  of  the  natives  of  Indoftan, 
and  whilft  himfelf  and  his  wife  go  into  the  woods,  to  collect 
leaves  and  branches  of  trees  for  his  food,  they  fix  him  to  the 
ground  by  a length  of  chain,  and  frequently  leave  a child  vet 
unable  to  walk,  under  its  proteffion  ; and  the  intelligent  animal 
not  only  defends  it,  but  as  it  creeps  about,  when  it  arrives  near 
the  extremity  of  his  chain,  he  wraps  his  trunk  gently  round  its 
body,  and  brings  it  again  into  the  centre  ot  his  circle.  Secondly, 
the  traitor  elephants  are  taught  to  walk  on  a narrow  path  be- 
tween two  pit-falls,  which  are  covered  with  turf,  and  then  to 
go  into  the  woods,  and  to  feduce  the  wild  elephants  to  come 
that  way,  who  fall  into  thefe  wells,  whilft  he  paftes  fafe  between 

them; 


OF  INSTINCT. 


103 


Sect.  XVI.  6. 

them:  and  it  is  univerfally  obferved,  that  thofe  wild  elephants 
that  efcape  the  fnare,  purfue  the  traitor  with  the  ti  tin  oft  vehe- 
mence, and  if  (hey  can  overtake  him,  which  lometimes  hap- 
pens, they  always  beat  him  to  death. 

The  monkey  has  a hand  well  enough  adapted  for  the  fenfe 
of  touch,  which  contributes  to  his  great  facility  of  imitation; 
but  in  taking  objects  with  his  hands,  as  a ftick  or  an  apple,  he 
puts  Iris  thumb  on  the  fame  hue  of  them  with  his  finger's,  inftead 
of  counteracting  the  pi  enure  of  his  fingers  with  it:  from  this 
negledt  he  is  much  flower  in  acquiring  the  figures  of  objedis, 
as  fie  is  lefs  able  to  determine  the  di  fiances  or  diameters  ot  their 
parts,  or  to  diftinguifh  their  vis  inertias  from  their  hardnefs. 
Helvetius  adds,  that  the  fhortnefs  of  his  life,  Iris  being  fugitive 
before  mankind,  and  his  not  inhabiting  ail  climates,  combine 
to  prevent  his  improvement.  (De  i’Efprit.  T.  1.  p.)  There 
Is,  however,  at . this  time,  an  old  monkey'-  {hewn  in  Exeter 
Change,  London,  who  having  loft  his  teeth,  when  nuts  are 
given  him,  takes  a ftone  into  his  hand,  and  cracks  them  with 
it  one  by  one : thus  ufmg  tools  to  efieft  his  purpofe  like  man- 
kind. 

The  beaver  is  another  animal  that  makes  much  ufe  of  his 
hands,  and  if  we  may  credit  the  reports  of  travellers,  is  pof- 
feffed  of  amazing  ingenuity.  This,  however,  M.  Buffon  af- 
firms, is  only  where  they  exift  in  large  numbers,  and  in  coun- 
tries thinly  peopled  with  men ; while  in  France,  in  their  fclitary 
ftate,  they  ftiew  no  uncommon  ingenuity; 

Indeed,  all  the  quadrupeds  that  have  collar-bones,  (clavi- 
cuire)  ufe  their  fore-limbs  in  fome  rneafure  as  we  ufe  cur  hands, 
as  the  cat,  fquirrel,  tyger,  bear  and  lion;  and  as  they  exerdfe 
the  fenfe  of  touch  more  univerfally  than  other  animals,  fo  are 
they  more  fagacious  in  watching  and  furprifing  their  prey.  All 
thole  birds  that  ufe  their  claws  for  hands,  as  the  hawk,  parrot, 
and  cuckoo,  appear  to  be  more  docile  and  intelligent;  though 
the  gregarious  tribes  of  birds  have  more  acquired  knowledge. 

Now,  as  the  images  that  are  painted  on  the  retina  of  the 
eye  are  no  other  than  figns,  which  recall  to  our  imaginations 
the  cbjefts  we  had  before  examined  by  the  organ  of  touch,  as 
is  fully  demon ftrated  by  Dr.  Berkley,  in  his  treadle  on  vifion; 
it  follows,  that  the  human  creature  has  greatly  more  accurate 
and  diftindl  fenfe  of  vifion  than  that  of  any  other  animal. 
Whence,  as  he  advances  to  maturity,  he  gradually  acquires  a 
fenfe  of  female  beauty,  which,  at  this  time,  directs  him  to  the 
object  of  his  new  paftion. 

Sentimental  love,  as  diftinguifhed  from  the  animal  paftion 
of  that  name,  with  which  it  is  frequently  accompanied,  con- 

lifts 


OF  INSTINCT. 


104 


Sect.  XVI.  6. 


lifts  in  the  defire  or  fenfation  of  beholding,  embracing,  and 
ifaluting  a beautiful  objedf. 

The  charadteriftic  of  beauty  therefore  is,  that  it  is  the  objedl 
of  love  ; and  though  many  other  objedls  are  in  common  lan- 
guage called  beautiful,  yet  they  are  only  called  fo  metapho- 
rically, and  ought  to  be  termed  agreeable.  A Grecian  temple 
may  give  us  the  pleafurable  idea  of  fublimity,  a Gothic  temple 
may  give  us  the  pleafurable  idea  of  variety,  and  a modem 
houfe  the  pleafurable  idea  of  utility  ; mufic  and  poetry'  may 
infpire  our  love  by  alfociation  of  ideas;  but  none  of  thefe,  ex- 
cept metaphorically,  can  be  termed  beautiful,  as  we  have  no 
wilhi  to  embrace  or  falute  them. 

Out  perception  of  beauty  conftfts  in  our  recognition,  by  the 
fenfe  of  vifion,  of  thofe  objedfs,  firft,  which  have  before  in- 
fpired  our  love  by  the  pleafure  which  they  have  afforded  to 
many  of  ourfenfes;  as  to  our  fenfe  of  warmth,  of  touch,  of 
fmell,  of  tafte,  hunger  and  third; ; and,  fecondly,  which  bear 
any  analogy  of  form  to  fuch  objedls. 

When  the  babe,  foon  after  it  is  born  into  this  cold  world,  is 
applied  to  its  mother’s  bofom,  its  fenfe  of  perceiving  warmth 
is  firft  agreeably  affected ; next  its  fenfe  of  fmell  is  delighted 
with  the  odour  of  her  milk  ; then  its  tafte  is  gratified  by  the 
flavour  of  it ; afterwards  tire  appetites  of  hunger  and  of  thirft 
afford  pleafure  by  the  poffeflion  of  their  objects,  and  by  the 
fubiequent  digeftion  of  the  aliment;  and,  laftly,  the  fenfe  of 
touch  is  delighted  by  the  foftnefs  and  fmoothnefs  of  the  milky 
fountain,  the  fource  of  fuch  variety  of  happinefs. 

All  thefe  various  kinds  of  pleafure  at  length  become  afloei- 
ated  with  the  form  of  the  mother’s  breaft;  which  the  infant 
embraces  with  its  hands,  preffes  with  its  lips,  and  watches 
with  its  eyes  ; and  thus  acquires  more  accurate  ideas  of  the 
form  of  its  mother’s  bofom,  than  of  the  odour  and  flavour,  at 
warmth,  which  it  perceives  by  its  other  fenfes.  And  hence,  at 
our  maturer  years,  when  any  objedl  of  villon  is  prefented  to 
us,  w'hich,  by  its  waving  or  ipiral  lines,  bears  any  limilitude  to 
the  form  of  the  female  bofom,  whether  it  be  found  in  a land- 
fcape  with  foft  gradations  of  riling  and  deicending  furface,  or 
in  the  forms  of  fome  antique  vales,  or  in  other  works  of  the 
pencil  or  the  chtffel,  we  feel  a general  glow  of  delight,  w hich 
feems  to  influence  all  our  fenfes  ; and,  if  the  objedt  be  not  too 
large,  we  experience  an  attradlion  to  embrace  it  with  our 
arms,  and  to  lalute  it  with  our  lips,  as  we  did  in  our  early  in- 
fancy the  bofom  of  our  mother.  And  thus  we  And,  according 
to  the  ingenious  idea  of  Hogarth,  that  the  waving  lines  of  beau- 
ty were  originally  taken  from  the  temple  of  Venus. 


This 


OF  INSTINCT, 


Sect.  XVI.  7. 


105 


This  animal  attraction  is  love ; which  is  a fenfation,  when 
the  object  is  prefent ; and  a delire,  when  it  is  abfent.  Which 
conftitutes  the  pureft  fource  of  human  felicity.  The  cordial 
drop  in  the  otherwife  vapid  cup  of  life,  and  which  overpays 
mankind  for  the  care  and  labour,  which  are  attached  to  the 
pre-eminence  of  his  lituation  above  other  animals. 

It  fhould  have  been  obferved,  that  colour,  as  well  as  form, 
fometimes  enters  into  our  idea  of  a beautiful  object,  as  a good 
complexion  for  inftance  ; becaufe  a tine  or  fair  colour  is  in  ge- 
neral a fign  of  health,  and  conveys  to  us  an  idea  of  the 
warmth  of  the  object;  and  a pale  countenance,  on  the  contra- 
ry, gives  an  idea  of  its  being  cold  to  the  touch. 

It  was  before  remarked,  that  young  animals  ufe  their  lips  to 
diftinguilh  the  forms  of  things,  as  well  as  their  fingers;  and 
hence  we  learn  the  origin  of  our  inclination  to  falute  beautif  ul 
objects  with  our  lips. 

VII.  There  are  two  ways  by  which  we  become  acquainted 
with  the  paffions  of  others  : firft,  by  having  obferved  the  effects 
of  them,  as  of  fear  or  angpr,  on  our  own  bodies,  we  know, 
at  fight,  others  are  under  the  influence  of  thefe  affections.  So, 
when  two  cocks  are  preparing  to  fight,  each  feels  the  feathers 
rife  round  his  own  neck,  and  knows,  from  the  fame  fign,  the 
difpofition  of  his  adverfary  : and  children,  long  before  they  can 
fpeak,  or  underhand  the  language  of  their  parents,  may  be 
frightened  by  an  angry  countenance,  or  foothed  by  fmiles  and 
blandi  (laments. 

Secondly,  when  we  put  ourfelves  in  the  attitude  that  any 
pafiion  naturally  occailons,  we  foon,  in  fome  degree,  acquire 
that  paffion ; hence,  when  thofe  that  fcold  indulge  themfelves 
in  loud  oaths,  and  violent  actions  of  the  arms,  they  increafe 
their  anger  by  the  mode  of  expreffing  themfelves;  and,  on  the 
contrary,  the  counterfeited  fmile  of  pleafure  in  difagreeable 
company,  foon  brings  along  with  it  a proportion  of  the  reality, 
as  is  well  illuftrated  by  Mr.  Burke.  (Effay  on  the  fubiime  and 
beautiful.) 

This  latter  method  of  entering  into  the  paffions  of  others  is 
rendered  of  very  exteniive  ufe  by  the  pleafure  we  take  in  imi- 
tation, which  is  every  day  prefented  before  cur  eyes,  in  the 
acSlions  of  children,  and  indeed  in  all  the  cuftoms  and  fafhions 
of  the  world.  From  this  our  aptitude  to  imitation  arifes,  what 
is  generally  underftood  by  the  word  fympathy,fo  well  explain- 
ed by  Dr.  Smith  of  Glafgow.  Thus  the  appearance  of  a 
clffeerful  countenance  gives  us  pleafure,  and  of  a melancholy 
one  makes  us  forrowful.  Yawning  and  fometimes  vomiting 
are  thus  propagated  by  fympathy ; and  fome  people  of  delicate 

fibres, 


OF  INSTINCT. 


Sect.  XVI.  8. 


ic6 

fibres,  at  the  prefence  of  a fpeCtacle  of  mifery,  have  felt  pain 
in  the  fame  parts  of  their  own  bodies  that  were  difeafed  or 
mangled  in  the  other.  Amongft  the  writers  of  antiquity, 
Ariftotle  thought  this  aptitude  to  imitation  an  eflential  property 
of  the  human  fpecies,  and  calls  man  an  imitative  animal. 

To  HOV 

Thefe,  then,  are  the  natural  ligns  by  which  we  underftand 
each  other,  and  on  this  (lender  bails  is  built  all  human  lan- 
guage. For  without  fome  natural  figns,  no  artificial  ones 
could  have  been  invented  or  underftood,  as  is  very  ingenioufly 
obferved  by  Dr.  Reid.  (Inquiry  into  the  Human  Mind.) 

VIII.  The  origin  of  this  univerfal  language  is  a fubject  of 
the  higheft  curiolity,  the  knowledge  of  which  has  always  been 
drought  utterly  inacceflible.  A part  of  which  we  fiiail,  how- 
ever, here  attempt. 

Light,  found,  and  odours,  are  unknown  to  the  foetus  in  the 
womb,  which,  except  the  few  fenfations  and  motions  already 
mentioned,  lleeps  away  its  time  infenGble  of  the  bufy  worid. 
But  the  moment  he  arrives  into  day,  he  begins  to  experience 
many  vivid  pains  and  pleafures  ; thefe  are,  ast  the  fame  time,  at- 
tended with  certain  mufcular  motions,  and  from  this  their  ear- 
ly and  individual  aflociation,  they  acquire  habits  of  occur- 
ring together,  that  are  afterwards  indifibluble. 

i.  Of  Fear. 

As  foon  as  the  young  animal  is  bom,  the  firft  important 
fenfations  that  occur  to  him,  are  occafioned  by  the  oppref- 
llon  about  his  praeccrdia  for  want  of  refpiration,  and  by  his 
hidden  tranfition  from  ninety-eight  degrees  of  heat  into  fo  cold 
a climate. — He  trembles,  that  is,  he  exerts  alternately  all  the 
mufcles  of'his  body,  to  enfranchife  himfelf  from  the  oppref- 
lion  about  his  bofom,  and  begins  to  breathe  with  frequent  and 
ihort  refpirations ; at  trie  fame  time  the  cold  contracts  his  red 
fkin,  gradually  turning  it  pale,  the  contents  of  the  bladder 
and  of  the  bowels  are  evacuated;  and  from  the  experience  of 
thefe  firft  difagreeable  fenfations,  the  paftion  of  fear  is  excited, 
which  is  no  other  than  the  expectation  of  difagreeable  fenfa- 
tions. This  early  aflociation  of  motions  and  fenfations  perults 
throughout  file ; the  paftion  of  fear  produces  a coid  and  pale 
fkin,  with  tremblings,  quick  refpiration,  and  an  evacuation  ot 
the  bladder  and  bowels,  and  thus  conllitutes  die  natural  or 
univerfal  language  of  this  paftion. 

On  obferving  a Canary  bird  this  morning,  January  28, 
1772,  at  the  houfe  of  Mr.  Harvey,  near  Tutbury,  in  Der- 
by (hire,  I was  told  it  always  fainted  away,  when  its  cage  was 

cleaned. 


Ssct.  XVI.  8, 


GF  INSTINCT. 


107 

cleaned,  and  deftred  to  fee  the  experiment.  The  cage  being 
taken  from  the  ceiling,  and  its  bottom  drawn  out,  the  bird  be- 
gan to  tremble,  and  turned  quite  white  about  the  root  cf  his 
bill : he  then  opened  his  mouth  as  if  for  breath,  and  reipired 
quick,  flood  ftraighter  up  on  his  perch,  hung  his  wings, 
ipread  his  tail,  doled  his  eyes,  and  appeared  quite  ffiff  and  ca- 
taleptic, for  near  half  an  hour,  and  at  length,  with  much  trem- 
bling and  deep  refpiration,  came  gradually  to  himfelf. 

2.  Of  Grief. 

That  the  internal  membrane  of  the  noftrils  may  be  kept  al- 
ways moift,  for  the  better  perception  of  odours,  there  are  two 
canals  that  conduit  the  tears,  after  they  have  done  their  office 
in  moiflening  and  cleaning  the  ball  of  the  eye,  into  a fack,  which, 
is  called  the  lacrymal  fack,  and  from  which  there  is  adudt  that 
opens  into  the  noftrils : the  aperture  of  this  duif  is  formed  of 
exquiftte  fenfibility ; and  when  it  is  ftimulated  by  odorous  parti- 
cles, or  by  the  drynefs  or  coldnefs  of  the  air,  the  fack  contrails 
itfelf,  and  pours  more  of  its  contained  moifture  on  the  organ  of 
fmell.  By  this  contrivance  the  organ  is  rendered  more  fit  for 
perceiving  fuch  odours,  and  is  preleived  from  being  injured  by 
thofe  that  are  more  ftrong  or  corroftve.  Many  other  receptacles 
of  peculiar  fluids  difgorge  their  contents,  when  the  ends  of 
their  duits  are  ftimulated  ; as  the  gall  bladder,  when  the  con- 
tents of  the  duodenum  ftimulate  the  extremity  of  the  common 
bileduil;  and  the  falivary  glands,  when  the  termination  of 
their  duils  in  the  mouth  are  excited  by  the  ftimulus  of  the  food 
we  mafticate.  Atque  veftculae  feminales  fuum  exprimunt  flui- 
dum  glande  penis  fricata. 

The  coldnefs  and  drynefs  of  the  atmofphere,  compared  with 
the  warmth  and  moifture  which  the  new-born  infant  had  juft 
before  experienced,  diiagreeably  afxedls  the  aperture  of  this 
lacrymal  lack : the  tears  that  are  contained  in  this  fack,  are 
poured  into  the  noftrils,  and  a further  fupply  is  fecreted  by  the 
lacrymal  glands,  and  diffufed  upon  the  eye-balls;  as  is  very 
viftble  in  the  eyes  and  noftrils  of  children  focn  after  their  na- 
tivity. The  fame  happens  to  us  at  our  maturer  age;  for  in 
fevere  frofty  weather,  fnivelling  and  tears  are  produced  by  the 
coldnefs  and  drynefs  of  the  air. 

But  the  lacrymal  glands,  which  feparate  the  tears  from  the 
blood,  are  lituated  on  the  upper  external  part  of  the  globes  of 
each  eye;  and,  when  a greater  quantity  of  tears  are  wanted, 
we  contract  the  forehead,  and  bring  down  the  eye-brews,  and 
ufe  many  other  diftortions  of  the  face,  to  comprels  thefe  glands. 

Now,  as  the  fuffocating  fenfation  that  produces  refpiration, 

CL  is 


OF  INSTINCT. 


Sect.  XVI.  8. 


1 08 

is  removed  almoft  as  foon  as  perceived,  and  does  not  recur 
again ; this  difagreeable  irritation  of  the  lacrymal  duels,  as  it. 
muft  frequently  recur,  till  the  tender  organ  becomes  uied  to  a. 
variety  of  odours,  is  one  of  the  firfl  pains  that  is  repeatedly 
attended  to  : and  hence,  thoughout  our  infancy,  and  in  many 
people  throughout  their  lives,  all  difagreeable  fenfations  are 
attended  with  fnivelling  at  the  nofe,  a profufion  of  tears,  and 
fome  peculiar  diftortions  of  countenance;  according  to  the 
laws  of  early  affociation  before  mentioned,  which  conftitute 
the  natural  or  univerfal  language  of  grief. 

You  may  allure  yourfelf  of  the  tiuth  of  this  obfervation,  if 
you  will  attend  to  what  pafies,  when  vou  read  a diftrefsful  tale 
alone : before  the  tears  overflow  your  eyes,  you  will  invari- 
ably feel  a titillation  at  that  extremity  of  the  lacrymal  dud 
which  terminates  in  the  nbftril  ; then  the  comprelficn  of  the 
eyes  fucceeds,  and  the  profulion  of  tears. 

Linnaeus  aflerts,  that  the  female  bear  fheds  tears  in  grid 
die  fame  has  been  faid  of  the  hind,  and  fome  other  animals. 

3.  Of  Tender  Pleafure. 

The  firft  mbit  lively  impreflion  of  pleafure  that  the  infant 
enjoys  after  its  nativity,  is  excited  by  the  odour  of  its  mother’s 
milk.  The  organ  of  fmell  is  irritated  by  this  perfume,  and  the 
lacrymal  lack  empties  itfelf  into  the  nofhils,  as  before  explain- 
ed, and  an  increale  of  tears  is  poured  into  the  eyes.  Any  one 
may  obferve  this,  when  very  young  infants  are  about  to  fuck  ; 
for,  at  thofe  early  periods  of  life,  the  fenlation  affeds  the  organ 
of  fmell  much  more  powerfully  than  after  the  repeated  ha- 
bits of  fuelling;  have  inured  it  to  odours  of  common  ftrengah : 
and  in  cur  adult  years,  the  ftronger  fmells,  though  they  are 
at  the  fame  time  agreeable  to  us,  as  of  volatile  fpirits,  continue 
to  produce  an  increafed  fecretion  of  tears. 

This  plealing  fenfation  of  fmell  is  followed  bv  the  earlv  afi- 
fedion  of  the  infant  to  the  mother  that  fuckles  it ; and  hence 
the  tender  feelings  of  gratitude  and  love,  as  well  as  of  hopclefs 
grief,  are  ever  alter  joined  with  die  titillation  of  the  extremity 
of  the  lacrymal  duds,  and  a profufion  of  tears. 

Nor  is  it  Angular,  that  the  lacrymal  fack  fhould  be  influ- 
enced by  plealing  ideas,  as  the  fight  of  agreeable  food  produces 
the  fame  effed  on  the  falivarv  glands.  Ac  dum  vidimus  in- 
fomniis  lafeivae  puellse  fimulacrum  tendirur  penis. 

Lambs  fhake  or  wriggle  their  tails,,  at  the  time  when  diev 
firft  luck,  to  get  ftee  of  the  hard  excrement  which  had  been 
long  lodged  in-  their  bowels.  Hence  this  becomes  afterwards 
a mark  of  pleafure  in  them,  and  in-dogs,  and  other  tailed  ani- 

41  mals. 


Sect.  XVI.  8. 


OF  INSTINCT. 


109 

mals.  But  cats  gently  extend  and  contrail  their  paws  when 
they  are  plealed,  and  purr,  by  drawing  in  their  breath,  both 
which  relemble  their  manner  of  fucking,  and  thus  become  their 
language  of  pleafure  ; for  thefe  animals  having  collar-bones, 
ufe  their  paws  like  hands  when  they  fuck,  which  dogs  and 
fheep  do  not. 

.4.  Of  Serene  Pleafure. 

In  the  adlion  of  fucking,  the  lips  of  the  infant  are  clofed 
around  the  nipple  of  its  mother,  till  he  has  filled  his  flomach, 
and  the  pleafure  occafioned  by  the  flimulus  of  this.grateful  food 
fucceeds.  Then  the  fphiniter  of  the  mouth,  fatigued  by  the 
continued  adfion  of  fucking,  is  .relaxed ; and  the  antagonift 
mufcles  of  the  face  gently  adling,  produce  the  fmile  of  plea- 
fure ; as  cannot  but  be  feen  by  all  who  are  converfant  with 
children. 

Hence  this  fmile,  during  our  lives,  is  affociated  with  gentle 
pleafure;  it  is  vifible  in  kittens  and  puppies,  when  they  are 
played  with  and  tickled  ; but  more  particularly  marks  the  hu- 
man features.  For  in  children  this  expreffion  of  pleafure  is 
much  encouraged,  by  their  imitation  of  their  parents,  or  friends, 
who  generally  addrefs  them  with  a finding  countenance : and 
hence  fome  notions  are  more  remarkable  for  the  gaiety,  and 
others  for  the  gravity  of  their  looks. 

5.  Of  Anger. 

The  adfions  that  conftitute  the  mode  of  ‘fighting,  are  the 
immediate  language  of  anger  in  all  animals  ; and  a preparation 
•for  thefe  adlions  is  the  natural  language  of  threatening.  Hence 
the  human  creature  clenches  his  fill;,  and  fternly  furveys  his 
.adverfary,  as  if  meditating  where  to  make  the  attack ; the  ram, 
and  the  bull,  draws  himfejf  fome  fteps  backwards,  and  levels  his 
horns ; and  thehorfe,as  he  fights  by  ftrikingwith  his  hinder  feet, 
turns  his  heels  to  his  foe,  and  bends  back  his  ears,  to  liften  out 
the  place  of  his  adverfary,  that  the  threatened  blow  may  not 
he  inffectual. 

6.  Of  Attention . 

The  eye  takes  in  at  once  but  half  our  horizon,  and  that  on- 
ly in  the  day  ; and  our  fmell  informs  us  of  no  very  diftant  ob- 
jects hence  we  confide  principally  in  the  organ  of  hearing  to 
apprize  us  of  danger  : when  we  hear  any  the  fmallefi:  found, 
that  we  cannot  immediately  account  for,  our  fears  are  alarmed, 
we  fufpend  curfteps,  hoid  every  mufcleftill,open  our  mouths  a 
little,  eredt  cur  ears,  and  lifien  to  gain  further  information : 
and  this  by  habit  becomes  the  general  language  of  attention  to 
objedls  of  fight,  as  well  as  of  hearing;  and  even  to  the  fuccef- 
five  trains  of  our  ideas. 

The 


no 


OF  INSTINCT. 


Sect.  XVI.  9. 

The  natural  language  of  violent  pain,  which  is  exprefied 
by  writhing  the  body,  grinning,  and  fcreaming ; and  that  of 
tumultuous  pleafure,  expreiTed  in  loud  laughter,  belong  to  Sec- 
tion XXXIV.  on  Difeafes  from  Volition. 

IX.  Id  muft  have  already  appeared  to  the  reader,  that  all 
other  animals,  as  well  as  man,  are  poffeffed  of  this  natural 
language  of  the  paffions,  expreiTed  in  iigns  or  tones  ; and  we 
fhall  endeavour  to  evince,  that  thofe  animals  which  have  pre- 
ferved  themfelves  from  being  enflaved  by  mankind,  and  are  af- 
fociated  in  flocks,  are  alfo  poffeffed  of  fome  artifleial  language, 
and  of  fome  traditional  knowledge. 

i he  mother-turkey,  when  fhe  eyes  a kite  hovering  high  in 
air,  has  either  feen  her  own  parents  thrown  into  tear  at  his 
prefence,  or  has,  by  obfervation,  been  acquainted  with  his 
dangerous  deligns  upon  her  young.  She  becomes  agitated  with 
fear,  andufes  the  natural  language  ot  that  paflion  ; her  young 
ones  catch  the  fear  by  imitation,  and  in  an  inftant  conceal 
themfelves  in  the  grafs. 

At  the  fame  time  that  Ihe  thews  her  fears  bv  her  geflure  and 
deportment,  the  ufes  a certain  exclamation,  Kce-ut,  Koe-uc ; 
and  the  young  ones  afterwards  know,  when  fney  hear  this  note, 
though  they  do  not  fee  their  dam,  that  the  prefence  of  their 
adverfary  is  denounced,  and  hide  themfelves  as  before. 

The  wild  tribes  of  birds  have  frequent  opportunities  oi  know- 
ing their*  enemies,  by  observing  the  deftruchon  they  make  a- 
mong  their  progeny,  of  which  every  vear  but  a imall  part  ef- 
capes  to  maturity  : but  to  ourdomeftic  birds  theie  opportunities 
fo  rarely  occur,  that  their  knowledge  or  their  diftant  enemies 
muft  frequently  be  delivered  by  tradition,  in  the  manner  above 
explained,  through  many  generations. 

This  note  of  danger,  as  well  as  the  other  notes  of  the  mother- 
turkey,  when  fhe  calls  her  flock  to  tlieir  food,  or  to  fleep  un- 
der her  wings,  appears  to  be  an  artificial  language,  both  as  ex- 
preffed  by  the  mother,  and  as  underftood  by  the  progeny.  For  a 
hen  teaches  this  language  with  equal  eafe  to  the  ducklings  ihe 
has  hatched  from  fuppolitious  eggs,  and  educates  as  her  own 
offsprng : and  the  wagtails,  or  hedge-fparrows,  learn  it  from  the 
young  cuckoo,  their  fofter  nurfling,  and  lupply  him  with  food 
long  after  he  can  fly  about,  whenever  they  hear  his  cuckoo- 
ing; which  Linnaeus  tells  us  is  his  call  of  hunger.  (Syll.  Nat.) 
And  all  our  domcftic  animals  are  readily  taught  to  come  to  us 
for  food,  when  we  ufe  one  tone  of  voice,  and  to  fly  from  our 
anger,  when  we  ufe  another. 

Rabbits,  as  they  cannot  eaflly  articulate  founds,  and  are  form- 
ed into  fooleries, -that  live  underground,  have  a very  different 

method. 


Sect.  XVI.  io. 


OF  INSTINCT. 


in 


method  of  giving  alarm.  When  danger  is  threatened,  they 
thump  on  the  ground  with  one  of  their  hinder  feet,  and  produce 
a found  that  can  be  heard  a great  way  by  animals  near  the 
furface  of  the  earth,  which  would  feem  to  be  an  artificial  tign 
both  from  its  Angularity  and  its  aptnefs.to  the  fituation  of  the 
animal. 

The  rabbits  on  the  ifland  of  Sor,  near  Senegal,  have  white 
flefh,  and  are  well  rafted,  but  do  not  burrow  in  the  earth,  fo 
that  we  may  fufpetff  their  digging  themfelves  houfes  in  this  cold 
climate  is  an  acquired  art,  as  well  as  their  note  of  alarm. 
(Adanfon’s  Voyage  to  Senegal.) 

The  barking  of  dogs  is  another  curious  note  of  alarm,  and 
would  feem  to  be  an  acquired  language,  rather  than  a natural 
ftgn : for,  “ in  the  ifland  of  Juan  Fernandes,  the  dogs  did  not 
attempt  to  bark,  till  fome  European  dogs  were  put  among 
them,  and  then  they  gradually  begun  to  imitate  them,  but  in 
a ftrange  manner  at  firft,  as  if  they  were  learning  a thing  that 
was  not  natural  to  them.”  (Voyage  to  South- America  by 
Don  G.  Juan,  and  Don  Ant.  de  Uiloa.  B.  2.  c.  4.) 

Linnaeus  alfo  obferves,  that  the  dogs  of  South-America  do 
not  bark  at  ftrangers.  (Syft.  Nat.)  And  the  European  dogs, 
that  have  been  carried  to  Guinea,  are  faid  in  three  or  four  ge- 
nerations to  ceafe  to  bark,  and  only  howl,  like  the  dogs  that 
are  natives  of  that  coaft.  (World  Difplayed,  vol.  xvii.  p.  26.) 

A circumftance  not  diffimilar  to  this,  and  equally  curious, 
is  mentioned  by  Kircherus  de  Mufurgia,  in  his  chapter  de 
Lufciniis.  “ That  the  young  nightingales,  that  are  hatched 
under  other  birds,  never  ftng  till  they  are  inftructed  by  the 
company  of  other  nightingales.”  And  Johnfton  affirms,  that 
the  nightingales  that  vifit  Scotland,  have  not  the  fame  harm-cny 
as  thole  of  Italy,  (Pennant’s  Zoology,  8vo.  p.  255;)  which 
would  lead  us  to  fufpedf,  that  the  finging  of  birds,  like  hu- 
man muftc,  is  an  artificial  language  rather  than  a natural  ex- 
preffion  of  paffion. 

X.  Our  mufic,  like  our  language,  is  perhaps  entirely  con- 
ftituted  of  artificial  tones,  which,  by  habit,  fuggeft  certain  agree- 
able paftions.  For  the  fame  combination  of  notes  and  tones 
do  not  excite  devotion,  love,  or  poetic  melancholy  in  a native 
of  Indoftan  and  of  Europe.  And  “ the  Highlander  has  the 
fame  warlike  ideas  annexed  to  the  found  of  a bagpipe  (an  in- 
ftrument  which  an  Englifhman  derides),  as  the  Englishman 
has  to  that  of  a trumpet  or  fife.”  (Dr.  Brown’s  Union  of  Po- 
etry and  Mufic,  p.  58.)  So  “ the  mufic  of  the  Turks  is  very 
different  from  the  Italian ; and  the  people  of  Fez  and  Moroc- 
co have  again  a different  kind,  which  to  us  appears  very  rough 

and 


OF  INSTINCT. 


112 


Sect.  XVI.  ro. 


and  horrid,  but  is  highly  pleafing  to  them.”  (L’  Arte  Armor 
niaca  a Giorgio  Antoniotto.)  Hence  we  fee  why  the  Italian 
opera  does  not  delight  an  untutored  Englishman ; and  why 
thofe  who  are  unaccuftomed  to  muGc  are  more  pleafed  with  a 
tune  the  fecond  or  third  time  they  hear  it,  than  the  firfl: : for 
then  the  fame  melodious  train  of  founds  excites  rhe  melanchcly 
they  had  learned  from  the  fong ; or  the  fame  vivid  combination 
of  them  recalls  all  the  mirthful  ideas  of  the  dance  and  company. 

Even  the  founds  that  were  once  difagreeable  to  us  mav,  bv 
habit,  be  affooiated  with  other  ideas,  fo  as  to  become  agreeable. 
Father  Lafitau,  in  his  account  of  the  Iroquois,  fays,  “ the  mufic 
and  dance  of  thofe  Americans  have  fomething  in  them  extremely 
barbarous,  which  at  firfl  dilgufis.  We  grow  reconciled  to  them 
•by  degrees,  and  in  the  end  partake  or  them  with  pleafure:  the 
favages  themfelves  are  fond  of  them  to  detraction.”  (Mceurs 
des  Savages,  tom.  ii.) 

There  are,  indeed,  a few  founds  that  we  very  generally  affo- 
ciate  with  agreeable  ideas,  as  the  whittling  of  birds,  or  purrin- 
of  animals,  that  are  delighted ; and  fome  others,  that  we  as  gene- 
rally affociate  with  difagreeable  ideas, as  the  cries  o;  animals  in 
pain,  the  hifs  of  feme  of  them  in  anger,  and  the  mid-night  howl 
of  beafts  of  prey.  Yet  we  receive  no  terrible  or  fublime  ideas 
from  the  lowing  of  a cow,  or  the  braying  of  an  afs;  which 
evinces,  that  thele  emotions  are  owing  to  previous  affociations. 
So,  it  the  rumbling  of  a carriage  in  the  ftreet  be  lor  a moment 
miftaken  for  thunder,  we  receive  a fublime  fenfation,  which 
ceafes  as  foon  as  we  know  ir  is  the  noife  ot  a coach  and  fix. 

There  are  other  difagreeable  founds,  that  are  faid  to  fet  the 
teeth  on  edge;  which,  as  they  have  always  been  thought  a ne- 
ceffary  effedt  of  certain  difeordant  notes,  become  a proper  fub- 
jedt  .of  our  enquiry.  Every  one  in  his  childhood  has  repeatedly 
bit  a part  of  the  glafs  or  earthen  vefiel,  in  which  his  food  has 
been  given  him,  and  has  thence  had  a very  difagreeable  fenfa- 
tion in  the  teeth ; which  fenfation  was  defigned  by  nature  to 
prevent  us  from  exerting  them  on  objects  harder  than  them- 
felves.  The  jarring  found  produced  between  the  cup  and  the 
teeth  is  always  attendant  on  this  difagreeable  fenlation  : and 
ever  after,  when  fuch  a found  is  accidentally  produced  by  the 
conflict  of  two  hard  bodies,  we  feel,  by  aflociation  of  ideas, 
the  concomitant  difagreeable  fenfation  in  our  teeth. 

Others  have  in  their  infancy  frequently  held  the  corner  of  a 
filk  handkerchief  in  their  mouth,  or  the  end  ot  the  velvet  cape 
of  their  coat,  whilft  their  companions  in  play  have  plucked  ir 
from  them,  and  have  given  another  difagreeable  fenfation  to 
their  teeth,  which  has  afterwards  recurred  cn  touching  thofe 

materials. 


Sect.  XVI.  ii. 


OF  INSTINCT. 


ii3 

materials.  And  the  fight  of  a knife  drawn  along  a china  plate, 
though  no  found  is  excited  by  it,  and  even  the  imagination  of 
fuch  a knife  and  plate  fo  fcraped  together,  I know,  by  repeated 
experience,  will  produce  the  fame  difagreeable  fenlation  of  the 
teeth. 

Thefe  circumftances  indifputably  prove,  that  this  fenfatir.n 
of  the  tooth-edge  is  owing  to  affociated  ideas  ; as  it  is  equally 
excitable  by  fight,  touch,  hearing,  or  imagination. 

In  refpeCl  to  the  artificial  proportions  of  found  excited  by 
muftcal  inflruments,  thole  who  have  early  in  life  affociated 
them  with  agreeable  ideas,  and  have  nicely  attended  to  diftin- 
guifh  them  from  each  other,  are  faid  to  have  a good  ear,  in 
that  country  where  fuch  proportions  are  in  fafhion  ; and  not 
from  any  fuperior  perfection  in  the  organ. of  hearing,  or  any 
iriftin&ive  fympathy  betwreen  certain  founds  and  paffions. 

I have  obferved  a child  to  be  exquifitely  delighted  with  mu- 
fic,  and  who  could  with  great  facility  learn  to  ling  any  tune 
that  he  heard  diftin&ly,  and  yet  whofe  organ  of  hearing  was  fo 
imperfeCt,  that  it  was  ncceffary  to  fpcak  louder  to  him  in  com- 
mon converfation  than  to  others. 

Our  mufic,  like  our  architecture,  feems  to  have  no  founda- 
tion in  nature ; they  are  both  arts  purely  of  human  creation,  as 
they  imitate  nothing.  And  the  profeffors  of  them  have  only 
elaffed  thofe  circumftances  that  are  moft  agreeable  to  the 
accidental  tafte  of  their  age,  or  country;  and  have  called  it 
Proportion.  But  this  proportion  muft  aiways  fluctuate,  as  it 
refts  on  the  caprices  that  are  introduced  into  our  minds  by  our 
various  modes  of  education.  And  thefe  fluctuations  of  tafte 
muft  become  more  frequent  in  the  prefent  age,  where  mankind 
have  infranchifed  themielves  from  the  blind  obedience  to  the 
rules  of  antiquity  in  perhaps  every  fcience,  but  that  of  archi- 
tecture. See  SeCt.  XII.  No.  7.  3. 

XI.  There  are  many  articles  of  knowdedge,  which  the  ani- 
mals in. cultivated  countries  feem  to  learn  very  early  in  their 
lives,  either  from  each  other,  or  from  expeiience,  or  cbferva- 
tion : one  of  the  moft  general  of  thefe  is  to  avoid  mankind. 
There  is  fo  great  a refemblancc  in  the  natural  'language  of  the 
paffions  of  all  animals,  that  we  generally  know  when  they 
are  in  a pacific,  or  in  a malevolent  humour  ; they  have  the 
fame  knowledge  of  us ; and  hence  we  can  fcold  them  from  ns 
byfome  tones  and  geftures,  and  could  pofftbly  attraCt  them  to 
us  by  others,  if  they  were  not  already  apprized  of  our  general, 
malevolence  towards  them.  Mr.  Gmelin,  profeffor  at  Peterf- 
burg,  affures  us,  that  in  his  journey  into  Siberia,  undertaken 
by  order  of  the  Emprefs  of  Ruffia,  he  faw  foxes  that  exprei- 


Ill 


OF  INSTINCT. 


Sect.  XVI.  n. 


fed  no  fear  of  himfelf  or  companions,  but  permitted  him  to 
come  quite  near  them,  having  never  ieen  the  human  creature 
before.  And  Mr.  Bougafnvilie  relate-,  that  at  his  arrival  at  the 
Malouine,  or  Falkland’s  iflands,  which  were  not  inhabited  bv 
men,  all  the  animals  came  about  himfelf  and  his  people;  the 
fowls  fettling  upon  their  headl  and  fhoulders,  and  the  quadru- 
peds running  about  their  feet.  From  the  difficulty  of  acquiring 
the  confidence  of  old  animals,  and  the  eafe  of  taming  young 
ones,  it  appears  that  the  fear  they  all  conceive  at  the  fight  of 
mankind,  is  an  acquired  article  of  knowledge. 

This  knowledge  is  more  nicely  underfiood  bv  rooks,  who 
are  formed  into  locieties,  and  build,  as  it  were,  cities  over  our 
heads;  they  evidently  diidinguifh,  that  the  danger  is  greater 
when  a man  is  armed  with  a gun.  Every  one  has  leen  this, 
who,  in  the  fpring  of  the  year,  has  walked  under  a rookery 
with  a gun  in  his  hand;  the  inhabitants  of  the  trees  rife  on 
their  wings,  and  feream  to  the  unfledged  young,  to  fhrink  in- 
to their  reids  from  the  fight  of  the  enemy.  The  vulgar,  ob- 
lerving  this  circumftance  fo  uniformly  to  occur,  alien  that 
rooks  can  fmell  gun-powder. 

The  fielufairs  (turdus  pilarus)  which  breed  in  Norway, 
and  come  hither  in  rhe  cold  feafon  for  our  winter  berries,  as 
they  are  affociated  in  flocks,  and  are  in  a foreign  country, 
have  evident  marks  of  keeping  a kind  or  watch,  to  remark  and 
announce  the  appearance  of  danger.  On  approaching  a tree, 
that  is  covered  with  them,  they  continue  fearlefs,  tiii  one  at 
the  extremity  of  the  bufh,  riling  on  his  wings,  gives  a loud  and 
peculiar  note  of  alarm,  when  they  all  immediately  fly,  except 
one  other,  who  continues  till  you  approach  ftiil  nearer,  to  cer- 
tify, as  it  were,  the  reality  of  the  danger,  and  then  he  alio  flies 
off  repeating  the  note  of  alarm. 

And  in  the  woods  about  Senegal  there  is  a bird  called  uett- 
uett  bv  the  negroes,  and  fquailers  by  the  French,  which,  as 
loon  as  they  lee  a man,  fet  up  a loud  feream,  and  keep  flying 
round  him,  as  if  their  intent  was  to  warn  other  birds,  which, 
upon  hearing  the  cry,  immediately  take  wing.  1 hefe  birds 
are  the  bane  of  fportfmen,  and  frequently  put  me  mto  a pai- 
iion,  and  obliged  me  to  ihoot  them.  (Adanlon’s  Voyage  to  Se- 
negal, 78).  For  the  fame  intent  the  leffer  birds  of  our  climate 
l'eern  to  fiv  after  a hawk,  cuckoo,  or  owl,  and  feream  to  pre- 
vent their  companions  from  being  fui  prifed  bv  die  general  ene- 
mies of  themfeives,  or  of  their  eggs  and  progeny. 

Eut  the  lap-wing,  (charadrius  pluvialis  Lin.)  when  her  un- 
fledged offspring  run  about  the  marines,  where  they  were 
hatched,  not  only  gives  the  note  or  alarm  at  the  approach  o: 

men 


OF  INSTINCT. 


Sect. XVI.  it. 


”5 


rnen  or  dogs,  that  her  young  may  conceal  themfelves ; but  fly- 
ing and  {creaming  near  the  adverfary,  fhe  appears  more  folici- 
tous  and  impatient  as  he  recedes  from  her  family,  and  thus  en- 
deavours to  miflead  him,  and  frequently  iucceeds  in  her  de- 
flgn.  Thefe  laft  inftances  are  fo  appofite  to  the  fituation,  ra- 
ther than  to  the  natures  of  the  creatures  that  ufe  them,  and 
are  fo  fnnilar  to  the  nations  of  men  in  the  fame  circumftances, 
that  we  cannot  but  believe,  that  they  proceed  from  a fnnilar 
principle. 

On  the  northern  coaft  of  Ireland  a friend  of  mine  faw  above 
a hundred  crows  at  once  preying  upon  muicles ; each  crow 
took  a rnufcle  up  into  the  air  twenty  or  forty  yards  high,  and 
let  it  fall  on  the  hones,  and  thus,  by  breaking  the  ihell,  got  pof- 
feflxon  of  the  animal. — A certain  philofopher  (I  think  it  was 
Anaxagoras)  walking  along  the  lea-fhore  to  gather  (hells,  one 
of  thefe  unlucky  birds  miftaking  his  bald  head  for  a hone,  drop- 
ped a fhell-fifh  upon  it,  and  killed  at  once  a philofopher  and 
an  oyfrer. 

Our  domeflic  animals,  that  have  fome  liberty,  are  alfc  pof- 
feffed  of  fome  peculiar  traditional  knowledge ; dogs  and  cats 
have  been  forced  into  each  other’s  fociety,  though  naturally 
animals  of  a very  different  kind,  and  have  hence  learned  from 
each  other  to  eat  the  knot-grafs,  when  they  are  fick,  to  pro- 
mote vomiting.  I have  feen  a cat  mihake  the  blade  of  barley 
for  this  grafs,  which  evinces  it  is  an  acquired  knowledge.  They 
have  alio  learnt  of  each  other,  to  cover  their  excrement  and 
urine ; about  a fpoonful  of  water  was  fpilt  upon  my  hearth 
from  the  tea-kettle,  and  I obferved  a kitten  cover  it  with  afhes. 
Hence  this  muft  alfo  be  an  acquired  art,  as  the  creature  mif- 
took  the  application  of  it. 

To  preierve  their  fur  clean,  and  efpecially  their  whi fleers, 
cats  wafh  their  faces,  and  generally  quite  behind  fheir  ears, 
yvery  time  they  eat.  As  they  cannot  l’ck  thofe  places  with 
their  tongues,  they  fli ft  wet  the  infide  of  the  leg  with  faliva, 
and  then  repeatedly  wafh  their  faces  with  it,  which  muft  ori- 
ginally be  an  effedt  of  reafoning,  bec'aufe  a means  is  ufed  to 
produce  an  effedt ; and  feems  afterwards  to  be  taught  or  ac- 
quired by  imitation,  like  the  greateft  part  of  human  arts. 

Thefe  animals  feem  to  poflfefs  fomething  like  an  additional 
fenfe  by  means  of  their  whifkers  ; which  have  perhaps  fome 
analogy  to  the  antennae  of  moths  and  butterflies.  The  whif- 
kers of  cats  confift  not  only  of  the  long  hairs  on  their  upper 
lips,  but  they  have  alio  four  or  five  leng  hairs  handing  up 
from  each  eyebrow,  and  alfo  two  or  thiee  on  each  cheek  ; all 
which,  when  the  animal  eredls  them,  make  with  their  points 

R fo 


OF  INSTINCT. 


Sect.  XVI.  i r. 


no 

fo  many  parts  of  the  periphery  of  a circle,  of  an  extent  at  leaf! 
equal  to  the  circumference  of  any  part  of  their  own  bodies. 
With  this  inflrument  I conceive,  by  a little  experience,  they 
can  at  once  determine  whether  any  aperture  among  ft  hedges 
or  fhrubs  im  which  animals  of  this  genus  live  in  their  wild  flare, 
is  large  enough- to  admit  their  bodies  ; which,  to  them,  is  a mat- 
ter of  the  greateft  confequence,  whether  purfuing  or  puriued. 
They  have  iikewife  a power  of  erecting  and  bringing  forward 
the  whifkers  on  their  lips;  which,  probably,  is  for  thepurpofe 
of  feeling  whether  a dark  hole  be  further  permeable. 

The  antenna,  or  horns,  of  butterflies  and  moths,  who  have 
awkward  wings,  the  minute  feathers  of  which  are  very  liable 
to  injury,  ferve,  I fuppofe,  a fimilar  purpofe  of  meafuring,  as 
they  fly  or  creep  amougft  the  leaves  of  p ants  and  trees,  whe- 
ther their  wings  can  pals  without  touching  them. 

Mr.  Leonard,  a very  intelligent  friend  of  mine,  faw  a cat 
catch  a trout  by  darting  upon  it  in  a deep  clear  water,  at  the 
mill  of  Weaford.  near  Litchfield.  The  cat  belonged  to  Mr. 
Stanley,  who  had  often  feen  her  catch  fifh  in  the  fame  manner 
in  fu miner,  when  the  mill-pool  was  drawn  fo  low  that  the  fifh 
could  be  feen.  1 have  heard  of  other  cats  taking  fifh  in  fhallow 
water,  as  they  flood  on  the  bank.  This  feems  a natural  art  of 
taking  their  prey  in  cats,  which  their  acquired  delicacy,  by  do- 
meftication,  has  in  general  prevented  them  from  ufing,  though 
their  deiire  of  eating  fifh  continues  in  its  original  ftrength. 

Mr.  White,  in  his  ingenious  hiftory  of  Seibourn,  was  wit- 
nefs  to  a cat  & ftickling  a young  hare,  which  followed  her  about 
the  garden,  and  came  jumping  to  her  call  of  affection.  At 
Liford,  near  Litchfield,  the  Rev.  Mr.  Sawley  had  taken  the 
young  ones  out  of  a hare,  which  was  fhot ; they  were  alive, 
and  the  cat,  who  had  juft  loft  her  own  kittens,  carried  them 
away,  as  it  was  luppoied,  to  eat  them;  but  it  prefen dy  ap- 
peared, that  it  was  affedlion,  not  hunger,  which  incited  her, 
as  fne  fueklcd  them,  and  brought  them-up  as  their  mother. 

Other  in  fiances  of  the  miflaken  application  of  what  has  been 
termed  inftidl  may  be  cbferved  in  flies  in  the  night,  who,  imiftak- 
ing  a candle  for  day-light,  approach,  and  perith  in  the  flame.— 
So  the  putrid  fmell  of  the  Ilapelia,  or  carrion-ficwdr,  allures 
the  large  flefn-fly  to  depolrt  its  young  worms  on  its  beautiful 
petals,  which  perith  there  for  want  of  nourishment.  This, 
therefore,  cannot  be  a neceffary  inflinril,  becauie  the  creature 
miftakes  the  application  of  it. 

Though  in  this  country  horfles  fliew  little  veftiges  of  policy, 
yet  in  the  defarts  of  Tartary  and  Siberia,  when  hunted  bv 
he  Tartars,  they  are  feen  to  form  a kind  of  community,  let 

watches 


Sect.  XVI.  it. 


OF  INSTINCT. 


i*7 

watches  to  prevent  their  "being  furprifed,  and  have  commanders, 
.who  direct,  andhuften  their  flight.  (Origin  of  Language,  voi.  i. 
p.  212.)  in  this  country,  where -four  or  five  horfes  travel  in  a 
line,  the  firft  always  points  his, ears  forward,  and  the  lad  points 
his  backward,  while  the  intermediate  ones  feetn  quite  carelefs- 
in  this  refpedt;  which  feems  a part  of  policy  to  prevent  fur- 
prife  ; as  all  animals  depend  rnof!  on  the  ear  to  apprize  litem 
of  the  approach  of  danger,  the  eyd  caking  in  only  half  the  ho- 
rizon at  once,  and  horfes  pofTefs  a great  nicety  of  this  lenle, 
as  appears  from  their  mode  of  fighting,  mentioned  .No.  8.  5. 
of  this  Se&ion,  as  weil  as  by  common  obferva-ion. 

There  are  fome  parts  of  a horfe,  which  he  cannot  conve- 
niently rub,  when  they  itch,  as  about  the  fhoulder,  which  he 
can  neither  bite  with  his  teeth,  nor  fcr'atch  with  his  hind  foot  ; 
when  this  part  itches,  he  goes  to  another  horfe,  and  gently 
bites  him  in  the  part  which  he  wifhes  to  be  bitten,  which  is  im- 
mediately done  by  his  intelligent  friend.  I once  obferved  a 
young  foal  thus  bite  its  large  mother,  who  did  not  chafe  to 
drop  the  grafs  fire  had  in  her  mouth,  and  rubbed  her  nofe  again!! 
the  foal’s  neck  in  (lead  of  biting  it;  which  evinces  that  (he 
knew  the  defign  of  her  progeny,  and  tv  as  not  governed  by  a 
neceffary  inftindf,  to  bite  where  fire  was  bitten. 

Many  of  our  fhrubs,  which  would  otherwife  afford  an 
agreeable  food  to  horfes,  are  armed  with  thorns  or  .prickles, 
which  lecure  them  from  thofe  animals ; as  the  holly,  hawthorn, 
goofeberry,  gorfe.  In  the  extenfive  moorlands  of  Staffordfhire, 
the  horfes  have  learnt  to  Lamp  upon  a gorfe-bufh,  with  one 
of  their  fore-feet,  for  a minute  together,  and  when  the  points 
are  broken,  they  eat  it  without  injury  ; which  is  an  arc  other 
horfes  in  the  fertile  parts  of  the  country  do  not  pofTefs,  and 
prick  their  mouths  fill  they  bleed,  if  they  are  induced  by  hun- 
ger or  caprice  to  attempt  eating  gorfe. 

Swine  have  a lenfe  of  touch  as- well  as  of  fmeil  at  the  end  of 
their  nofe,  which  they  ufe  as  a hand,  both  to  root  up  the  foil, 
and  to  turn  over  and  examine  objects  of  food,  fomewhat  like 
the  probofcis  of  an  elephant.  As  they  require  fhelter  from  the 
cold  in  this  climate,  they  have  learnt  to  colled!  ftraw  in  their 
mouths  to  make  their  neft,  when  the  wind  blows  cold  ; and 
to  call  their  companions  by  repeated  cries  to  affif!  in  the  work, 
and  add  to  their  warmth  by  their  numerous 'bed-fellows.  Hence 
thefe  animals,  which  are  efteemed  io  unclean,  have  alfo  learned 
never  to  befoul  their  dens,  where  they  have  liberty,  with  them 
own  excrement ; an  art  which  cows  and  horfes,  which  have 
open  hovels  to  run  into,  have  never  acquired.  I have  obferved 
great  iagacity  in  fwine ; but  the  fhort  lives  we  allow  them,  and 

their 


OF  INSTINCT. 


Sect.  XVI.  12. 


nB 

their  general  confinement,  prevents  their  improvement,  which, 
might  probably  be  Otherwife  greater  than  that  of  dogs. 

Inftances  of  the  fagacity  and  knowledge  of  animals  are  very 
numerous  to  every  obferveri  and  their  docility  in  learning  va- 
rious arts  from  mankind,  evinces  that  they  may  learn  fimilar 
arts  from  their  own  fpecies,  and  thus  be  pofiefled  of  much  ac- 
quired and  traditional  knowledge. 

A dog,  whofe  natural  prey  is  Iheep,  is  taught  bv  mankind, 
not  only  to  leave  them  unmolefted,  but  to  guard  them  ; and 
10  hunt,  to  fet,  or  to  defiroy  other  kinds  of  animals,  as  birds, 
or  vermin  ; and,  in  fome  countries,  to  catch  filh ; in  others,  to 
find  truffles,  and  to  pradtife  a great  varietv  of  tricks  : is  it  more 
furprifmg  that  the  crows  fhould  teach  each  other,  that  the  hawk 
can  catch  lefs  birds,  bv  the  fuperior  fwiftneis  of  his  wing,  and 
if  two  of  them  follow  him,  till  he  fucceeds  in  his  defign,  that 
they  can  by  force  fhare  a part  of  the  capture  ? This  I have  for- 
merly obferved  with  attention  and  aftonifhment. 

There  is  one  kind  of  pelican  mentioned  by  Mr.  Ofbeck,  one 
of  Linnaeus’s  travelling  pupils,  (the  pelicanus  acquilm)  whofe 
food  is  filli ; and  which  it  takes  from  other  birds,  becaufe  it  is 
not  formed  to  catch  them  itielf ; hence  it  is  called  bv  the  Eng- 
liih,  a man-of-war  bird.  (Voyage  to  China,  p.  88.)  There 
are  many  other  interefting  anecd  tes  of  the  pelican  and  cor- 
morant, coliedled  from  authors  ot  the  bell  authority,  in  a, 
well-managed  Natural  Hiltory  for  Cnildren,  publilhed  by  Mr. 
Galton.  Johnfon.  London. 

And  the  following  narration,  from  the  very  accurate  Monf. 
Adanfon,  in  his  voyage  to  Senegal,  may  gain  credit  with  the 
reader,  as  his  employment  in  this  country  was  folely  to  make 
obfervations  in  natural  hiftory.  On  the  river  Niger,  in  his 
road  to  the  ifland  Griel,  lie  law  a great  number  of  pelicans, 
or  wide  throats.  “ They  moved  with  great  flate,  like  fwaiis 
upon  the  water,  and  are  the  largeff  biid  next  to  the  clinch; 
the  bill  of  the  one  I kiile  , was  upwards  of  a foot  and  hair  long, 
and  the  bag  faflened  underneath  it  held  two-and-tweniy  pints 
of  water.  They  fwim  in  flocks,  and  form  a large  circle,  which 
they  comradt  afterwards,  driving  the  filli  before  them  with 
their  legs  : when  they  fee  the  flfli  in  fufficient  number  confined 
in  this  Ipace,  they  plunge  their  bill  wide  open  into  the  water, 
and  fhut  it  again  with  great  quicknefs.  They  thus  get  filh 
into  their  throat-bag,  which  they  eat  afterwards  on  lliore  at 
their  ieil'ure.”  Page  247. 

XII.  The  knowledge  and  language  of  thofe  birds,  that  fre- 

O OO 

quently  change  their  annate  with  the  ieaions,  are  ft;  11  mere  ex- 
teuiive ; as  they  perform  thele  migrations  in  large  loaem-g 


OF  INSTINCT. 


Sect.  XVI.  12. 


119 


and  are  lefs  fubjecr  to  the  power  of  man,  than  the  refident 
tribes  of  birds.  They  are  laid  to  follow  a leader  during  the 
day,  who  is  occafionally  changed,  and  to  keep  a continual  cry 
during  the  night  to  keep  themlelves  together.  It  is  probable  that 
thefe  emigrations  were  at  hrft  undertaken  as  accident  directed, 
by  the  more  adventurous  of  their  fpecies,  and  learned  from  one 
another  like  the  difcoveries  of  mankind  in  navigation.  The 
following  circumftances  dronglv  iupport  this  opinion. 

1.  Nature  has  provided  thefe  animals,  in  the  climates  where 
they  are  produced,  with  another  refource,  when  the  feafon 
becomes  too  cold  for  their  conditutions,  or  the  lood  they  were 
iupported  with  ceafes  to  be  fupplied : I mean  that  of  deeping. 
Dormice,  fnakes,  and  bats  have  not  the  means  of  changing  then- 
country  ; the  two  former  from  the  want  of  wings,  and  the  lat- 
ter from  his  being  not  able  to  bear  the  light  of  the  day.  Hence, 
thefe  animals  are  obliged  to  make  ufe  or  this  refource,  and 
fleep  during  the  winter.  And  thofe  fwallows  that  have  been 
hatched  too  la\e  in  the  year  to  acquire  their  full  drength  of  pi- 
nion, or  that  have  been  maimed  by  accident  or  diieaie,  have 
been  frequently  found  in  the  hollows  of  rocks  on  the  fea  coafts, 
and  even  under  water  in  this  torpid  date,  from  which  they  have 
been  revived  by  the  warmth  of  a fire.  This  torpid  date  of 
fwallows  is  tedided  by  innumerable  evidences,  both  of  ancient 
and  modern  names.  A'ridotle,  fpeaking  of  the  fwallows,  fays, 
“ They  pafs  into  warmer  climates  in  winter,  if  fuch  places  are 
at  no  great  didance  ; if  they  are,  they  bury  themfelves  in  the 
climates  where  they  dwell.”  (8  Hid.  c.  16.  See  alfo  Der- 
ham’s  Phyf.  Theol.  ii.  p.  177.) 

Hence  their  emigrations  cannot  depend  on  a necejfary  in- 
dindt,  as  the  emigrations  themfelves  are  not  hecejjary  ! 

2.  When  the  weather  becomes  cold,  the  fwallows  in  the 
neighbourhood  ademble  in  large  flocks;  that  is,  the  unexperi- 
enced attend  thofe  that  have  bef  ore  experienced  the  journey  they 
are  about  to  undertake:  they  are  then  feen  fome  time  to  hover 
on  the  coad,  till  there  is  calm  weather,  or  a wind  that  fuits 
the  direction  of  their  flight.  Other  birds  of  padage  have  been 
drowned  by  thoufands  in  the  fea,  or  have  fettled  on  fhips,  quite 
exhauded  with  fatigue.  And  others,  either  by  midaking  their 
courfe,  or  by  didrefs  of  weather,  have  ai  rived  in  countries  where 
they  were  never  feen  before,  and  thus  are  evidently  fubjedl  to 
the  lame  hazards  that  the  human  Ipecies  undergo,  in  the  exe- 
cution of  their  artidcial  purpofes. 

3.  The  lame  birds  are  emigrant  from  fome  countries,  and 
not  fo  from  others;  the  fwallows  were  feen  at  Goree,  in  Ja- 
nuary, by  an  ingenious  philofopher  of  my  acquaintance,  and  he 

was 


no  OF  INSTINCT.  Sect.XVI.i2. 

was  told  that  they  continued  there  all  the  year  ; as  the  warmth 
of  the  climate  was  at  all  feafons  fufficient  for  their  own  comf 1- 
tutions,  and  for  the  production  of  the  flies  that  fuppiy  them  with 
cnourilhment.  Herodotus  fays,  that  in  Lybia,  about  the  fprings 
of  the  Nile,  the  fwallows  continue  all  the  year.  (L.  2.) 

Quails  (tctrao  corturnix,  Lin.)  are  birds  of  paffige.  from  the 
could  of  Barbary  to  Italy,  and  have  frequently  fettled  in  large 
ihoals,  on  {hips,  fatigued  with  their  flight.  (Ray.  Wiidoir.  of 
God,  p.  129.  Durham  Phytic.  Theol.  vol.  ii.  p.  178.)  Dr. 
Ruffe!,  in  his  Hiftory  of  Aleppo,  obferves,  that  the  fwallows 
Vifit  that  country  about  the  end  of  February,  and  having 
hatched  their  young,  difappear  about  the  end  of  July;  and,  re- 
turning again  about  the  beginning  of  October,  continue  about 
a fortnight,  and  then  again  difappear.  (P.  70.) 

When  my  late  friend  Dr.  Chambers,  of  Derby,  was  on  the 
illand  of  Caprea,  in  the  bay  of  Naples,  he  was  informed  that 
great  flights  of  quails  annually  fettle  on  that  ifland,  about  the 
beginning  of  May,  in  their  paffage  from  Africa  to  Europe. 
And  that  they  always  come  -when  the  fouth-eaft  wind  blows, 
are  fatigued  when  they  reft  on  this  ifland,  and  are  taken  in  fuch 
amazing  quantities,  and  fold  to  the  continent,  that  die  inhabit- 
ants pay  the  bifhop  his  ftipend  out  of  the  profits  ariling  from 
the  fale  of  them. 

The  flights  of  thefe  birds  acrofs  the  Mediterranean  are  re- 
corded near  three  thoufand  years  ago.  “ There  went  forth  a 
wind  from  the  Lord,  and  brought  quails  from  the  lea,  and  let 
them  fall  upon  the  camp,  a day’s  journey  round  about  it,  and 
they  were  two  cubits  above  the  earth.”  ( N umb.  ii.  31.) 

In  our  country,  Mr.  Pennant  informs  us,  that  i'ome  quails 
migrate,  and  others  only  remove  from  the  internal  parts  of  the 
ifland  to  the  coatls.  (Zoology,  octavo,  2 10.)  Some  of  the  ring- 
doves and  flares  breed  here,  others  migrate.  (Ibid.  510,  511.) 
Amd  the  {lender  billed  imallbirds  do  not  all  quit  thele  kingdoms 
in  the  winter,  though  the  difficulty  of  procuring  the  worms  and 
infedfs  that  they  feed  on,  Applies  the  fame  reafon  for  migra- 
tion to  them  all.  (Ibid.  51 1.) 

Linnaeus  has  oblerved,  that  in  Sweden  the  female  chaffinches 
quit  that  country  in  September,  migrating  into  Holland,  and 
leave  their  mates  behind  till  their  return  in  the  fpring.  Hence 
he  has  called  them  Fringiila  caslebs.  (Am$n.  Acad.  ii.  42.  iv. 
595.)  Now,  in.  our  climate,  both  fexes  of  diem  are  perennial 
birds.  And  Mr.  Pennant  obferves,  that  the  hoopoe,  chatterer, 
hawfinch,  and  crofshili,  migrate  into  England  fo  rareiv,  and  at 
fuch  uncertain  times,  as  not  to  Jeferve  to  be  ranked  among  our 
birds  of  paffage.  (Ibid.  51 1.) 


The 


OF  INSTINCT. 


22 2 


Sect.  XVI.  13. 

The  water  fowl,  as  geefe  and  ducks,  are  better  adapted  for 
long  migrations,  than  the  other  tribes  of  birds,  as,  when  the 
weather  is  calm,  they  cannot  only  reft  themfelves,  or  fleep  up- 
on the  ocean,  but  poffibly  procure  feme  kind  of  food  from  it. 

Hence,  in  Siberia,  as  loon  as  the  lakes  are  frozen,  the  water- 
fowl, which  are  very  numerous,  ail  diiappear,  and  are  luppofed 
to  fly  to  warmer  climates,  except  the  rail,  which,  from  its  in- 
ability for  long  flights,  probably  fieeps,  like  our  bat,  in  their 
winter.  The  following  account,  from  the  journey  of  Profei- 
for  Gmelin,  may  entertain  the  reader.  “ In  the  neighbour- 
hood of  Krafnoiark,  amongff  many  other  emigrant  water  fowls, 
weobferved  a great  number  of  rails,  which,  when  purl'ued,  ne- 
ver took  flight,  but  endeavoured  to  efc'ape  by  running.  We 
enquired  how  there  birds,  that  could  not  fly,  couid  retire  into 
other  countries  in  the  winter,  and  were  told,  both  by  the  Tartars 
and  Aflanians,  that  they  wTeil  knew  thofe  birds  could  not  alone 
pafs  into  other  countries  ; but  when  the  crains  (les  grues)  re- 
tire in  autumn,  each  one  takes  a rail  (un  rale)  upon  his  b„ck, 
and  carries  him  to  a warmer  climate.” 

Recapitulation. 

1.  All  birds  of  paflage  can  exil'd  in  the  climates  where  they 
are  produced. 

2.  They  are  fubjedd,  in  their  migrations,  to  the  fame  accidents 
and  difficulties  that  mankind  axe  fubjedd:  to- in  navigation. 

3.  The  fame  fpecies  of  birds  migrate  from  dome  countries, 
and  are  refldent  in  others. 

From  all  thefe  eircumfdances  it  appears,  that  the  migrations 
of  birds  are  not  produced  by  a neceffary  in  (din  61,  but  are  acci- 
dental improvements,,  like  the  arts  among  mankind,  taught  by 
the  r cctemporaries,  or  delivered,  by  tradition,  Irom  one  gene- 
ration of  them  to  another. 

XIII.  In  that  feafon  of  the  year  which  fupplies  the  nouri (la- 
ment proper  for,  the  expedited  brood,  the  birds  enter  into  a contradb 
of  marriage,  and,  with  joint  labour,  confdrucd  a bed  for  the 
reception  of  their  offspring.  Their  choice  of  the  proper  feafon, 
their  contradds  of  marriage,  and  the  regularity  with  which  they 
confbudd  their  nefts,  have  in  all  ages  excited  the  admiration 
of  naturaiifts  ; and  have  always  been  attributed  to  the  power  of 
inftindd,  which,  like  the  ocult  qualities  of  the  ancient  phiioio- 
phers,  prevented  all  further  enquiry.  W e Ahull  conlider  them 
in  their  order. 

Their  Choice  of  the  Seafon. 

Our  domefdic  birds  that  are  plentifully  fupplied  throughout 
the  year  with  their  adapted  food,  and  are  covered  with  houies 

from 


122 


OF  INSTINCT. 


Sect.  XVI.  ij. 

from  the  inclemency  of  the  weather,  lay  their  eggs  at  anv  fea- 
fon ; which  evinces  that  the  i'pring  of  the  year  is  not  pointed 
otic  to  them  by  a neceffarv  iriftindL 

Whilft  the  wild  tribes  of  birds  choofe  this  time  of  the  year 
from  their  acquired  knowledge,  that  the  mild  temperature  of 
the  air  is  more  convenient  for  h itching  their  eggs,  and  is  loon 
likely  to  fupply  that  kind  of  nourilhment  that  is  wanted  for 
their  young. 

If  the  genial  warmth  of  the  fpririg  produced  the  paffion  of 
love,  as  it  expands  the  foliage  of  trees,  ail  other  animals  fhoukl 
feel  its  influence  as  well  as  birds;  but,  the  viviparous  creatuies, 
as  they  fuckle  their  young,  that  is,  as  they  previoufly  digefl  the 
natural  food,  that  it  may  better  luit  the  tender  ftomachs  ot  their 
offspring,  experience  the  influence  of  this  paffi on  at  all  leafons 
of  the  year,  as  cats  and  bitches.  The  graminivorous  animals, 
indeed,  generally  produce  their  young  about  the  time  when  grais 
is  fupplied  in  the  greatell  plenty;  but  this  is  without  any  degree 
of  exaclnefs,  as  appears  from  our  cows,  fheep,  and  hares,  and 
may  be  a part  of  the  traditional  knowledge  which  they  learn 
from  the  example  of  their  parents. 

Their  Contracts  of  Marriage. 

Their  mutual  paffion,  and  their  acquired  knowledge,  that 
their  joint  labour  is  neceffarv  to  procure  fuftenance  mr  their 
numerous  family,  induce  the  wild  birds  to  enter  into  a con- 
trail of  marriage,  which  does  not,  however,  take  place  among 
the  ducks,  geefe,  and  fow  ls,  that  are  provided  with  their  daily 
food  from  our  barns. 

An  ingenious  philofopher  has  lately  denied  that  animals  can 
enter  into  contrails,  and  thinks  this  an  effential  difference  be- 
tween them  and  the  human  creature  : but  does  not  daily  ob- 
fervation  convince  us,  that  they  form  contrails  ot  friend  (hip 
with  each  other,  and  with  mankind?  When  puppies  and  kit- 
tens play  together,  is  there  not  a tacit  contrail,  that  they  will 
not  hurt  each  other  ? And  does  not  your  favourite  dog  expect 
vou  fhould  give  him  his  daily  food,  for  his  lervices  and  atten- 
tion to  you,  and  thus  barters  his  love  for  vour  proteilicn  in  the 
fame  manner  that  all  contrails  are  made  amongft  men  that  do 
not  underhand  each  other’s  arbitrary  language  ? 

The  ConJlruRlon  of  ihelr  Thefts. 

x.  They  feetn  to  he  initruiled  how  to  build  their  nefls  from 
their  obfervation  ot  that  in  which  thevw  ere  educated,  and  from 
their  knowledge -of  thofe  things  that  are  moil  agreeable  to  their 
touch  in  leipeil  to  warmth,  cleanlinei's  and  liability.  They 

choole 


OF  INSTINCT. 


Sect1.  XVI.  13. 


123 


choofe  their  Situations  from  their  ideas  of  fafety  from  their  ene- 
mies, and  of  fhelter  frorti  the  weather.  Nor  is  the  colour  of  their 
nefts  a cirCumftance  unthought  of;  the  finches,  that  build  in 
green-hedges,  cover  theirhabitations  with  green  mofs ; the  fwal- 
!ow  or  martin,  that  builds  again  ft  rocks  and  houfes,  covers  her’s 
with  clay ; whilft  the  lark  choofes  vegetable  ft  raw  nearly  of  the 
colour  of  the  ground  fhe  inhabits : by  this  contrivance,  they  are 
all  lefs  liable  to  be  difcovered  by  their  adverlaries. 

2.  Nor  are  the  nefts  of  the  fame  fpecies  of  birds  conftrucfed 
always  of  the  fame  materials,  nor  in  the  fame  form  ; which  is 
another  cireumftance  that  ascertains  that  they  are  led  by  ob- 
fervation. 

In  the  trees  before  Mr.  Levet’s  houfe,  in  Litchfield,  there 
are  annually  nefts  built  by  fparrows,  a bird  which  ufually  builds 
under  the  tiles  of  houfes,  or  the  thatch  of  barns.  Not  finding 
fuch  convenient  lituations  for  their  nefts,  they  build  a covered 
neft  bigger  than  a man’s  head,  with  an  opening  like  a mouth  at 
the  fide,  refembling  that  of  a magpye,  except  that  it  is  built  with 
ftraw  and  hay,  and  lined  with  feathers,  and  io  nicely  managed 
as  to  be  a defence  againft  both  wind  and  rain. 

So  the  jackdaw  (corvus  moneduia)  generally  builds  in  church 
fteeples,  or  under  the  roofs  01  high  houfes ; but  at  Sclbourn,  in 
Southamptonlhire,  where  towers  and  fteeples  arenotfufficiencly 
numerous,  thefe  fame  birds  build  in  lorfaken  rab.c  burrows. — 
See  a curious  account  of  thefe  Subterranean  nefts  in  White’s 
Hiftory  of  Selbourn,  p.  59.  Can  the  fkiifui  change  of  architec- 
ture in  thefe  birds  and  the  fparrows  above  mentioned  be  govern- 
ed by  inftindt?  Then  they  mull  have  two  in  Hindis,  one  for 
common,  and  the  other  for  extraordinary  occaficns. 

I have  feen  green  worded  in  a neft,  which  no  where  exifts 
in  nature;  and  the  down  of  thi Ties  in  thofe  nefts  that  were 
by  feme  accident  conftrucfed  later  in  the  fummer,  which 
material  could  not  be  procured  for  the  earlier  nefts:  in  many 
different  climates  they  cannot  procure  the  fame  materials  that 
they  ufe  in  ours.  And  it  is  well  known,  that  the  Canary 
birds,  that  are  propagated  in  this  country,  and  the  finches, 
that  are  kept  tame,  will  build  their  nefts  of  any  flexile  ma- 
terials that  are  given  them.  Plutarch,  in  his  Book  on  Rivers, 
fpeaking  of  the  Nile,  fays,  “ that  the  fwallows  celled!  a ma- 
terial, when  the  waters  recede,  with  which  they  form  nefts, 
that  are  impervious  to  water.”  And  in  India  there  is  a lwallow 
that  colledts  a glutinous  fubftance  for  this  purpofe,  whole  neft: 
is  eiculent,  and  efteemed  a principal  rarity  amongft  epicures. 
(Lin.  Syft.  Nat.)  Both  thefe  muft  beconftrudtecl  ot  very  differ- 
ent materials  from  thofe  ufed  by  the  fwallows  of  our  country. 

S la 


OF  INSTINCT 


124 


Sect.  XVI.  1 3. 


In  India  the  birds  exert  more  artifice  in  building  their  nefls, 
on  accdanf  of  the  monkeys  and  fnakes:  fome  form  their  pen- 
file  nefls  in  the  fhape  of  a purfe,  deep,  and  open  at  the  top  ; 
others  with  a hole  in  the  fide ; and  others,  {fill  more  cautious, 
with  an  entrance  at  the  very  bottom,  forming  their  lodge  near 
the  fummit.  But  the  taylor-bird  will  not  ever  trufl  its  nell  to 
the  extremity  of  a tender  twig,  but  makes  one  more  advance 
to  fafety,  bv  fixing  it  to  the  leaf  itfelf.  It  picks  up  a dead  leaf, 
and  fews  it  to  the  fide  of  a living  one  ; its  fiender  bill  being  its 
neeaie,  and  its  thread  fome  fine  fibres  ; the  lining  conlifls  of  fea- 
thers, goffamer,  and  down ; its  eggs  are  white,  the  colour  of 
the  bird  fight  yellow;  its  length  three  inches,  its  weight  three  fif- 
teenths of  an  ounce;  fo  that  the  materials  of  the  nefl  and  the 
weight  of  the  bird  are  not  likelv  to  draw  down  an  habitation 
fo  flightly  impended.  A nefl  of  this  bird  is  preferred  in  the  Bri- 
tifh  mufeuvn.  (Pennant’s  Indian  Zoology).  'I  bis  calls  to  one’s 
mind  the  Mofaic  account  of  the  origin  of  mankind , the  firfl 
dawing  of  art  there  afciibed  to  them,  is  that  of  fewing  leaves  to- 
gether. For  many  other  curious  kinds  of  nefls,  fee  Natural 
Hiflory  for  Children,  by  Pvlr.  Galton.  Johnfon.  London. 
Part.  I.  p.  47.  Gen.  Oriolus. 

3.  Thole  birds  that  arc  brought  up  by  our  care,  and  have 
had  little  communication  with  others  ot  their  own  fpecies,  are 
very  deiefilive  in  this  acquired  knowledge  ; they  are  not  only- 
very  awkward  in  the  conltruction  of  their  nells,  but  generally 
fcatter  their  eggs  in  various  parts  ot  the  room  01  cage,  w here 
they  are  confined,  and  feldotn  produce  young  ones,  till,  by  tail- 
ing in  their  firil  attempt,  they  have  learnt  fometiiing  from  their 
own  obfervation, 

4,  During  the  time  of  incubation  birds  are  faid  in  general 
ro  turn  their  eggs  every  day;  lome  cover  them,  when  they 
leave  the  nefl,  as  ducks  and  geele  ; in  fome  the  male  is  laid  to 
bring  food  to  the  female,  that  file  may  have  lefs  eccafion  ofab- 
fence  ; in  others  lie  is  faid  to  take  her  place,  when  the  gees  in 
ouefi  of  food ; and  all  ot  them  are  laid  to  leave  their  e>u>s  a 
ihorter  time  in  cold  weather  than  in  warm.  In  Senegal  the 
oftrich  fits  on  her  eggs  only  during  the  night,  "leaving  them  in 
the  day  to  the  heat  of  e-he  fun ; but  at  the  Cape  of  Good  Hope, 
where  the  heat  is  lets,  fine  fits  on  them  day  and  ni  lit. 

If  it  finouid  be  afked,  w'hat  induces  a bird  to  fit  weeks  on  its 
firfl  eggs  uncon'cious  that  a brood  of  young  ones  will  be  die 
product  ? The  an  fiver  mufl  be,  that  it  is  the  lame  pafiicn  that 
induces  the  human  mother  to  hold  her  offspring  whole  niciits 
and  days  in  her  fond  arms,  and  prefs  it  to  her  boiom,  uncoil - 
feious  of  its  tuture  growth  to  feme  and  manhood,  till  obferva- 
tion or  tradition  have  informed  her 


5.  And 


OF  INSTINCT. 


Sect.  XVI.  14. 


125 


5.  And  as  many  ladies  are  too  refined  to  nurfe  their  own 
children,  and  deliver  them  to  the  care  and  provilion  of  others  ; 
fo  is  there  one  inftance  of  this  vice  in  the  feathered  world. — 
The  cuckoo,  in  fome  parts  of  England,  as  I am  well  informed 
by  a very  diftin<£t  and  ingenious  gentleman,  hatches  and  edu- 
cates her  own  young;  whilft  in  other  parts  the  builds  no  neft, 
but  ufes  that  of  fome  leiTer  bird,  generally  either  of  the  wag- 
tail, or  hedge  fparrow,  and  depofiting  one  egg  in  it,  takes  no  fur- 
ther care  of  her-  progeny. 

As  the  Rev.  Mr.  Stafford  was  walking  in  Glofop  Dale,  in 
the  Peak  of  Derby (hire,  he  law  a cuckoo  rue  from  its  neft. 
The  neft  w7as  on  the  flump  of  a tree,  that  had  been  feme  time 
felled,  among  fome  chips  that  were  in  part  turned  grey,  fo  as 
much  to  refemble  the  colour  of  the  bird  ; in  this  neft  were  two 
. young-cuckoos : tying  a firing  about  tne  leg  of  one  of  them,  be 
pegged  the  other  end  of  it  to  the  ground,  and  very  frequently 
for  many  days  beheld  the  old  cuckoo  feed  thefe  her  young,  as 
he  flood  very  near  them. 

Nor  is  this  a new  obfervation,  though  it  is  entirely  overlooked 
by  the  modern  natural! fls  ; for  Ariftotie,  fpeaking  of  the  cuckoo, 
afferts  that  fhe  fometimes  builds  her  neft  among  broken  rocks-, 
and  on  high  mountains;  (L.  6.  H.  c.  1.)  but  adds,  in  another 
place,  that  fire  generally  p'ofTeiTes  the  neft  of  another  bird.  (L. 
6.  H.  c.  7,)  And  Niphus  fays,  that  cuckoos  rarely  build  for 
themfelves,  moll  frequently  laying  their  eggs  in  the  nefts  of  other 
birds.  (Gefner,  L.  3.  de  Cuculo.) 

The  phi lofopher  who  is  acquainted  with  thefe  facts  concerning 
the  cuckoo,  would  feem  to  have  very  little  reafon  himfelf,  if  he 
could  imagine  this  neglefil  of  her  young  to  be  a neceffary  inflindl; 

XIV.  The  deep  receffes  of  the  ocean  are  inacc-eflible  to 
mankind,  which  prevents  us  from  having  much  knowledge  o'f 
the  arts  and  government  ofits  inhabitants. 

1.  One  of  the  baits  ufed  by  the  fifherman  is  an  animal  called 
an  Old  Soldier:  his  fize  and  form  are  fome  what  like  the  craw- 
fi£h,  with  this  difference,  that  his  tail  is  covered  with  a tough 
membrane  inflead  cf  a fhell ; and  to  cbviate  this  defeat,  he  fecks 
out  the  uninhabited  fhell  of  fome  dead  fifh,  that  is  large  enough 
to  receive  his  tail,  and  carries  it  about  with  him  as  part  of  his 
clothing  or  armour. 

2.  On  the  coafts  about  Scarborough,  where  the  haddocks, 
cods,  and  dog-fifh  are  in  great  abundance,  the  filhermen  uni- 
verfaily  believe  jhat  the  dog-fifh  make  a line,  or  iemicircie,  to 
encompals  a fhoal  of  haddocks  and  cods,  confining  them  within 
certain  limits  near  the  fhore,  and  eating  them  as  cccaLcn  re- 
quires. for  the  haddocks  and  cods  are  always  found  near  the 
fhore  without  any  dog-fifh  among  them,  and  thedog-filb  fur- 
ther 


J2& 


OF  INSTINCT. 


Sect.  XVI.  \/r 

tlier  e fr,  without  any  haddocks  or  cod ; and  yet  the  former  are 
known  to  prey  upoathe  latter,  and  in  feme  years  devour  fuch 
immenfe  quantities  as  to  render  this  ffihery  mere  expert. ve 
than  profitable. 

3.  The  remora,  when  lie  willies  to  remove  his  fituation,  as 
he  is  a very  flow  fvvnnroer,  is  content  to  take  an  outfide  place 
on  whatever  conveyance  is  going  his  wav ; nor  can  the  cunning 
animal  be  tempted  to  quit  his  hold  of  a ib.ip  when  {he  is  failing, 
not  even  for  the  lucre  of  a piece  of  porkj  left  it  fhouid  endanger 
tile  lofs  of  his  p iff  age : at  ether  times  he  is  eafily  caught  with 
the  hook. 

4.  The  crab-fifh,  like  many  other  tefitaceous  animals,  an- 
nually changes  its  {hell;  it  is  then  in  a ioft  ftate.  covered  only 
with  a mucous  membrane,  and  conceals  itfelf  in  holes  in  the 
land  or  under  weeds:  at  this  place  a hard-fhelled  crab  always 
Hands  centinel,  to  prevent  the  lea  infects  from  injuring  the  other 
in  its  defencelefs  ftate ; and  the  fiihermen,  horn  his  appearance, 
know  where  to  find  the  loft  ones,  which  they  uie  for  baits  in 
catching  other  fifh. 

And  though  the  hard-fhelled  crab,  when  he  is  on  this  duty, 
advances  boldly  00  meet  the  foe,  and  will  with  difficulty  quit  the 
field  ; yet  at  other  times  he  (hews  great  timiditv,  and  has  a won- 
derful fpeed  in  attempting  his  elcape;  and,  if  often  interrupted, 
will  pretend  death  like  the  fpider,  and  watch  an  opportunity 
*0  fink  himfelf  into  the  fund,  keeping  only  his  eyes  above. — 
My  ingenious  friend  Mr.  Burdett,  who  favoured  me  with  thefe 
accounts  at  the  time  lie  was  furveying  the  coal  ts,  thinks  the  c ; m- 
xnerce  between  thefexes  takes  place  at  this  time,  and  m'.pires  the 
courage  of  the  creature. 

5.  The  fhoals  of  herrings,  cods,  haddocks,  and  oilier  hfh, 
which  approach  our  fhcres  at  certain  feafons,  and  quit  diem 
at  other  feafons  without  leaving  one  behind,  and  the  iaimon, 
that  periodically  frequent  our  rivers,  evince,  that  there  arc  va- 
grant tribes  of  fifh,  that  perform  as  regular  migrations  as  the 
birds  of  pafikge  already  mentioned. 

6.  There  is  a cataradl  on  the  river  LifFey,  in  Ireland,  about 
nineteen  feet  high  ; here,  in  the  falmon  feafon,  many  ot  the  in- 
habitants amufe  themfelves  in  observing  thefe  fifh  leap  up  the 
torrent.  They  dart  themfelves  quite  cut  of  the  water  as  they 
afeend,  and  frequently  fall  back  many  dines  be.' ore  ,hev  tur- 
mount  it ; and  bafkets  made  of  twigs  are  placed  near  the  edae 
of  the  ftre-nm  to  catch  them  in  their  fall. 

I have  obferved,  as  1 have  fat  by  a fpout  of  water,  which  de- 
scends from  a ftone  trough  about  two  feet  into  a Stream  below, 
at  particular  feafons  of  the  year,  a great  number  of  little  fi.h 
' ‘ " • called 


OF  INSTINCT. 


m 


Sect.  XVI.  15. 


called  minums,  or  pinks,  throw  themfelves  about  twenty  times 
their  own  length  out  of  the  water,  expecting  to  get  into  the 
Trough  above. 

This  evinces  that  the  ftorgee,  or  attention  of  the  darn  to  provide 
for  the  offspring,  is  drongly  exerted  amongft  the  nations  of  fifh, 
where  it  would  feem  to  be  the  mod  negledfed ; as  thefe  falmcn 
cannot  be  fuppofed  to  attempt  fo  difficult  and  dangerous  a talk 
without  being  confcious  of  the  purpofe  or  end  ot  their  endea- 
vours. 

It  is  further  remarkable,  that  mod  of  the  old  falmon  return 
to  the  fea  before  it  is  proper  for  the  young  Inoals  to  attend 
them ; yet,  that  a few  old  ones  continue  in  the  rivers  fo  late, 
that  they  become  perfectly  emaciated  by  the  inconvenience  of 
their  lituation,  and  this  apparently  to  guide  or  protect  the  un- 
experienced brood. 

Of  the  fmaller  water  animals  we  have  dill  lefs  knowledge, 
who  neverthelefs  probably  poffefs  many  fuperior  arts  ; fome  of 
thefe  are  mentioned  in  Botanic  Garden,  P.  I.  Add.  Note  XXVII. 
and  XXVIII.  The  nyinpha  of  the  water-moths  of  our 
rivers,  which  cover  themfelves  with  cafes  of  draw,  gravel,  and 
ihell,  contrive  to  make  their  habitations  nearly  in  equilibrium 
with  the  water : when  too  heavy,  they  add  a bit  ot  wood  or 
ftraw;  when  too  light,  a bit  of  gravel.  Edinb.  Tranf. 

All  thefe  circumdances  bear  a near  relemblance  to  the  de- 
liberate actions  of  human  reafon. 

XV.  We  have  a very  imperfecff  acquaintance  with  the  various 
tribes  of  infeeds : their  occupation,  manner  of  life,  and  even  the 
number  of  their  ferries,  differfrom  our  own,  and  from  each  other  ; 
but  there  is  reafon  to  imagine,  that  thofe  which  poffefs  the  fenfe 
of  touch  in  the  molt  exquiute  degree,  anu  whofe  occupations 
require  the  mod  condant  exertion  of  their  powers,  are  endued 
with  a greater  proportion  of  knowledge  and  ingenuity. 

The  fpiders  of  this  country  manufacture  nets  of  various 
forms,  adapted  to  various  dtuations,  to  arred  the  dies  that  are 
their  food;  and  fome  of  them  have  a houfe  or  lodging-place  in 
the  middle  of  the  net,  well  contrived  for  warmth,  fecurity,  or 
concealment.  There  is  a large  fpider  in  South- America,  who 
eondrucls  nets  of  fo  drong  a texture  as  to  entangle  fmall  birds, 
particularly  the  humming  bird.  And  in  Jamaica  there  is  ano- 
ther fpider,  who  digs  a hole  in  the  earth,  obliquely,  downwards, 
about  three  inches  in  length,  and  one  inch  in  diameter : this  ca- 
vity {he  lines  with  a tough  thick  web,  which,  when  taken  out, 
r-sfembles  a leathern  purfe  : but  what  is  mod  curious,  this  houfe 
has  a door  with  hinges,  like  the  operculum  of  fome  fea-fhells ; 
and  herfelf  and  family,  who  tenant  this  ned,  open  and  dvut  the 

door, 


OF  INSTINCT. 


12% 


Sect.  XVI.  i c. 


door,  whenever  they  pafs  or  repafs.  This  hiftory  was  tokl  me, 
and  die  neft,  with  its  operculum,  {hewn  me  by  the  late  Dr.  Butt 
of  Bath,  who  was  feme  years  phyfician  in  Jamaica. 

The  production  of  thefe  nets  is  indeed  a part  of  the  nature 
or  conformation  of  the  animal,  and  their  natural  life  :i  to  fup- 
ply  the  place  of  wings,  when  (lie  withes  to  remove  to  another 
fituation.  But  when  he  employs  them  to  entangle  her  prey, 
there  are  marks  of  evident  defign;  for  he  adapts  the  form  of  each 
net  to  its  fituation,  and  ft  ten  y hens  thofe  lines  that  require  it, 
by  joining  others  to  the  middle  of  them,  and  attaching  thefe 
others  to  diftant  objects,  with  the  fame  individual  art  that  is 
tired  by  mankind  in  fupporring  die  mafts  and  extending  the  fails 
of  hips.  Tiiis  work  is  executed  with  more  mathematical  ex- 
aftnefs  and  ingenuity  'ov  the  field  fpiders,  than  by  thole  in  our 
houftes,  as  their  ccnftruftions  are  more  fubjefted  to  the  injuries 
of  dews  and  tempefts. 

Betides  the  ingenuity  hewn  bvthefe  little  creatures  in  taking 
their  prey,  the  circumftance  of  their  counterfeiting  death,  w hen 
they  are  put  into  terror,  is  truly  wonderful ; and  as  ioon  as  the 
obi  eft  of  terror  is  removed,  they  recover  and  run  away.  Some 
beetles  are  alfo  faid  to  poffefs  this  piece  of  nypocrify. 

The  curious  webs,  or  chords,  conftrufted  by  fome  young 
caterpillars  to  defend  themfelves  from  cold,  or  from  infects  of 
prey  ; and  by  filk-worms  and  fome  other  caterpillars,  wlien 
they  tranfmi grate  into  aurelisor  larvae,  have  defervedly  excit- 
ed the  admiration  of  the  inquifitive.  But  our  ignorance  of 
their  manner  g£ life,  and  even  of  the  number  of  their  lerbes,  to- 
tally precludes  us  from  undemanding  the  means  by  which  thev 
acquire  this  knowledge. 

The  care  of  the  iaimon  in  chufing  a proper  fituation  for  her 
fpawn,  the  ftrufture  ot  the  nefts  of  birds,  their  patient  incuba- 
tion, and  the  art  of  the  cuckoo  in  depofiting  her  egg  in  her 
neighbour’s  nurfery,  are  inftances  ot  great  lagacitv  in  tin  fe 
creatures ; and  yet  they  are  much  inferior  to  the  arts  exerted  i>v 
many  of  the  infect  tribes  on  iimilar  occafions.  The  hairy  ex- 
crefcences  on  briars,  the  oak  apples,  the  klafted  leaves  ot  trees, 
and  the  lumps  on  the  backs  of  cows,  are  fituatious  that  are  ra- 
ther produced  than  chofen  by  the  mother  infeft  for  the  conve- 
nience of  her  offspring.  The  cells  of  bees,  wafps,  fpiders,  and 
of  the  various  eoraline  in- efts,  equally  aftonilh  us,  whether 
we  attend  to  the  materials  or  to  the  architecture. 

But  the  conduft  of  the  ant,  and  of  fome  fpecies  of  the  ich- 
neumon-fly in  the  incubation  of  their  eggs,  is  equal  to  any  ex- 
ertion of  human  fcience.  The  ants,  many  times  in  a day,  move 
their  eggs  nearer  the  iurface  of  their  habitation,  or  deeper  be- 
low 


OF  INSTINCT. 


Sject.  XVI.  1 6. 


129 


low  it,  as  the  heat  of  the  weather  varies ; and  in  colder  days  lie 
upon  them  in  heaps  for  the  purpofe  of  incubation  : if  their  man- 
lion  is  too  dry,  they  carry  them  to  places  where  there  is  moif- 
ture,  and  you  may  diftindUy  fee  the  little  worms  move  and  fuck 
up  the  water.  When  too  much  mcifture  approaches  their  neft, 
they  convey  their  eggs  deeper  in  the  earth,  or  to  fome.  other 
place  of  lafety.  (Swammerd.  Epil.  ad  Hift.lnfedts,  p.  153.  Pirih 
Tranf.  No.  23.  Lowthrop.  V.  2.  p.  7.) 

There  is  one  ipecies  of  ichneumon-fly  that  digs  a hole  in  the 
earth,  and  carrying  into  it  two  or  three  living  caterpillars,  de- 
posits her  eggs,  and  nicely  doling  up  the  nefc  leaves  them  there ; 
partly,  doubtiefs,  to  affift  the  incubation,  and  partly  to  fupply 
food  to  her  future  young.  (Derham.  B.  4.  c.  13.  Ariftotle  HifL 
Animal,  L.  5.  c.  2c.) 

A friend  or  mine  put  about  fifty  large  caterpillars,  collected 
from  cabbages,  on  fome  bran,  and  a few  leaves,  into  a box,  and 
covered  it  with  gauze  to  prevent  their  etcape.  After  a few  days 
we  faw,  from  more  than  three-fourths  of  them,  about  eight  or  ten 
little  caterpillars  of  the  ichneumon-fly  come  out  of  their  backs, 
and  fpin  each  a frnall  cocoon  of  filk,  and  in  a few  days  the  large 
caterpillars  died.  This  fmail  fly,  it  feems,  lays  it  egg  in  tire  back 
of  the  cabbage  cate:  pillar,  which,  when  hatched,  preys  upon  the 
material,  which  is  produced  there  for  the  purpofe  of  making  filk 
for  the  future  neil  of  the  cabbage  catterpillar  ; of  which  being- 
deprived,  the  creature  wanders  about  till  it  dies,  and  thus  our 
gardens  are  preferved  by  the  ingenuity  of  this  cruel  fly.  This 
curious  property  of  pioducinga  filk  thread,  which  is  common  to 
fome  iea  animals,  fee  Botanic  Garden,  Part  I.  Note  XXVII. 
and  is  defigned  tor  the  purpofe  of  their  transformation,  as  in  the 
filk- worm,  is  uled  for  conveying  themfelves  from  higher  bran- 
ches to  lower  ones  of  trees,  by  fome  caterpillars,  and  to  make 
themfelves  temporary  nefts  or  tents  ; and  by  the  fpkier  for  en- 
tangling his  prey.  Nor  is  it  Grange  that  fo  much  knowledge 
fhould  be  acquired  by  Inch  {mail  animals ; fmce  there  is  reafcn 
to  imagine,  that  thefe  iniedls  have  the  feme  of  touch,  either  in 
their  probofcis,  or  their  antennae,  to  a great  degree  of  perfec- 
tion ; and  thence  may  pofTefs,  as  far  as  their  fphere  extends,  as 
accurate  knowledge,  anti  as  lu-bde  invention,  as  the  difeoverers 
of  human  arts. 

XVI.  1.  It  v/e  were  better  acquainted  with  the  hi  dories  of 
thoie  1 niedts  that  are  formed  into  fcciet-ies,  as  the  bees,  walps,  and 
ants,  I make  no  doubt  but  we  fhould  find,  that  their  arts  and  im- 
provements are  not  io  limiiar  and  uniform  as  they  now  appear 
to  us,  but  that  they  arofe  in  the  fame  manner  from  experience 
and  tradition,  as  the  arts  of  our  own  Ipecies ; though  their  rea- 

foning 


OF  INSTINCT. 


13° 


Sect.  XVI.  16. 


foiling  is  from  fewer  ideas,  is  bufied  about  fewer  objects,  and  is 
exerted  with  lefs  energy. 

There  are  feme  kinds  of  infedts  that  migrate  like  the  birds  be- 
fore mentioned.  The  locuft  ot  warmer  climates  has  fometimes 
come  over  to  England  ; it  is  fhaped  like  a grafshopper,  with  ve- 
ry large  wings,  and  a body  above  an  inch  in  length.  It  is  men- 
tioned as  coming  into  Egypt  with  an  eaft  wind : “ The  Lord 
brought  an  eaft  wind  upon  the  land  all  that  day  and  night,  and 
in  the  morning  the  eaft  wind  brought  the  locufts,  and  covered 
the  face  of  the  earth,  fo  that  the  land  was  dark.”  Exod.  x.  13. 
The  migrations  of  thefe  infects  are  mentioned  in  another  part 
of  die  feripture : “ The  locufts  have  no  kings,  yet  go  they  forth 
all  of  them  in  bands.”  Prov.  xxx.  27. 

The  accurate  Mr.  Adanfon,  near  the  river  Gambia,  in  Africa, 
was  witnefs  to  the  migration  of  thefe  infedts.  “ About  eight  in 
the  morning,  in  the  month  of  February,  there  fuddenly  afofe 
over  our  heads  a thick  cloud,  which  darkened  the  air  and  de- 
prived us  of  the  rays  of  the  fun.  W e found  it  was  a cloud  of 
locufts,  raifed  about  twenty  or  thirty  fathoms  from  the  ground, 
and  covering  an  extent  of  feveral  leagues:  at  length  a I ho  we? 
of  thefe  infedls  defeended,  and  after  devouring  every  green  herb, 
while  they  refted,  again  relumed  their  flight.  This  ciond  was 
brought  by  a ftrong  eaft  wind,  and  was  ail  the  morning  in  pal- 
ling over  the  adjacent  country.”  (Voyage  to  Senegal,  158.} 

In  this  country  the  gnats  are  fometimes  feen  to  migrate  in 
clouds,  like  the  mufketoes  of  warmer  climates  ; and  our  lwarms 
of  bees  frequently  travel  many  miles,  and  are  laid  in  North- 
America  always  to  fly  towards  the  fouth.  The  prophet  Ifaiah 
has  a beautiful  alluiion  to  thefe  migrations:  “ The  Lord  ftiaii 
call  the  fly  from  the  rivers  of  Egypt,  and  fhail  hii's  for  the  bee 
that  is  in  the  land  of  Affyria,”  lia.  vii.  18.  which  has  been  late- 
ly explained  by  Mr.  Eruce,  in  his  travels  to  difeover  the  l'ource 
of  the  Nile. 

2.  I am  well  informed  that  the  bees  that  were  carried  into 
Barbadoes,  and  other  weftern  iflands,  ceaied  to  lay  up  any  ho- 
ney after  the  firft  year,  as  they  found  it  not  ufeful  to  titan ; and 
are  now  become  very  troublefome  to  the  inhabitants  of  thofe  if- 
lands, by  infefting  their  fugar  heufes ; but  thofe  in  Jamaica  con- 
tinue to  make  honev,  as  the  cold  north*  winds,  or  rainy  fea- 
fens  of  that  iitand,  confine  them  at  home  for  feveral  weeks  to- 
gether. And  die  bees  of  Senegal,  which  differ  from  thole  ot 
Europe  only  in  fize,  make  their  honey  not  only  fuperior  to  ours 
in  delicacy  of  flavour,  but  it  has  this  Angularity,  that  it  never 
concretes,  but  remains  liquid  as  fyrup.  (Adanfon).  From  lone 
obfervations  of  Mr.  Wildman,  and  of  other  people  of  veracity. 


Sect.  XVI.  16, 


OF  INSTINCT. 


^31 

it  appears,  that  during  the  fevere  part  of  the  winter  feafon,  for 
weeks  together,  the  bees  are  quite  benumbed  and  torpid  from  the 
cold,  and  do  not  confume  any  of  their  proviiion.  T his  flare  of 
fleep,  like  that  of  fwallows  and  bats,  feems  to  be  the  natural  re- 
fource  of  thofe  creatures  in  cold  climates,  and  the  making  of 
honey  to  be  an  artificial  improvement. 

As  the  death  of  our  hives  of  bees  appears  to  be  owing  to  their 
being  kept  fo  warm  as  to  require  food  when  their  flock  is  ex- 
haufted,  a very  obferving  gentleman,  at  my  requefl,  put  two 
hives  for  many  weeks  into  a dry  cellar,  and  obferved,  during 
all  that  time,  they  did  not  confume  any  of  their  provifion,  for 
their  weight  did  not  decreafe,  as  it  had  done  when  they  w'ere 
kept  in  the  open  air.  The  fame  obfervation  is  made  in  the 
Annual  Regiller  for  1768,  p.  1 13.  And  the  Rev.  Mr.  White, 
in  his  method  of  preferving  bees,  adds,  that  thofe  on  the  north 
fide  of  his  houfe  confumed  lefs  honey  in  the  winter  than  thofe 
' on  the  fouth  fide. 

There  is  another  obfervation  on  bees  well  afcertained,  that 
they,  at  various  times,  when  the  feafon  begins  to  be  cold,  by 
a general  motion  of  their  legs,  as  they  hang  in  clufters,  pro- 
duce a degree  of  warmth,  which  is  eafily  perceptible  by  the 
hand.  Hence,  by  this  ingenious  exertion,  they,  for  a long 
time,  prevent  the  torpid  ftate  they  would  naturally  fall  into. 

According  to  the  late  obfervations  of  Mr.  Hunter,  it  appears 
that  the  bees-wax  is  not  made  from  the  dull  of  the  anthers  of 
flowers,  which  they  bring  home  on  their  thighs,  but  that  this 
makes  wha  is  termed  bee-bread,  and  is  ufed  tor  the  purpofe  of 
feeding  the  bee-maggots ; in  the  fame  manner  butterflies  live  on 
honey,  but  the  previous  caterpillar  lives  on  vegetable  leaves, 
while  the  maggots  of  large  flies  require  flefh  for  their-food,  and 
thofe  of  the  ichneumon-fly  require  infedls  for  their  food.  What 
induces  the  bee,  who  lives  on  honey,  to  lay  up  vegetable  proven- 
der for  its  young?  What  induces  the  butterfly  to  lay  its  eggs  on 
leaves,  when  itfelf  feeds  on  honey  ? What  induces  the  other  flies 
to  feek  a food  for  their  progeny  different  from  what  they  con- 
fume themfelves  ? If  thefe  are  not  deductions  from  their  own 
previous  experience  or  obfervation,  all  the  adtions  of  mankind 
muft  be  refolved  into  inflindt. 

3.  “ Thedormoufe  confumes  but  little  of  its  food  during  the 
rigour  of  the  feafon,  for  they  roll  themfelves  up,  or  fleep,  or  lie 
torpid  the  greateft  part  of  the  time ; but  on  warm  funny  days 
experience  a fhort  revival,  and  take  a little  food,  and  then  relapfe 
into  their  former  ftate.”  (Pennant’s  Zoology,  p.  67.)  Other 
animals  that  fleep  in  winter,  without  laying  up  any  provender, 
are  obferved  to  go  into  their  winter  beds  fat  and  llrong,  but 

T return 


OF  INSTINCT, 


Sect. XVI.  id'. 


return  to  day -light,  in  the  fpring  feafon,  very  lean  and  feebleijl 
The  common  flies  fleep  during  the  winter  without  any  provifion 
for  their  nourishment,,  and  are  daily  revived  by  the  warmth  of  ’ 
the  fun  or  of  our  fires.  Thefe,  whenever  they  fee  light,  endea- 
vour to  approach  it,  having  obferved,  that  by  its  greater  vicinity 
they  get  free  from  the  degree  of  torpor  that  the  cold  produces  ; ' 
and  are  hence  induced  perpetually  to  burn  themfelves  in  cur 
candies;  deceived,  like  mankind,  by  the  mifapplication  of  their 
knowledge.  Whilft  many  of  the  Subterraneous  infedfs,  as  the 
common  worms,  feem  to  retreat  fo  deep  into  the  earth,  as  not  | 
to  be  enlivened  or  awakened  by  the  difference  of  our  winter  «. 
days  ; and  flop  up  their  holes  with  leaves  or  ftraws,  to  pre- 
vent  the  frofh  from  injuring  them,  or  the  centioes  from  devour-  ] 
ing  them.  The  habits  of  peace,  or  the  firatagems  of  war,  of 
thefe  fubterranean  nations,  are  covered  from  our  view  ; but  a 
friend  of  mine  prevailed  on  a diftreffed  worm  to  enter  the  hole  ' 
of  another  worm  on  a bowling-green,  and  he  prefently  return-  J 
ed  much  wounded  about  his  head.  And  I once  faw  a worm 
rife  haftily  out  of  the  earth  into  the  funihine,  and  obferved  a 
centipes  hanging  at  his  tail;  the  centipes  nimbly  quitting  the 
tail,  and  feizing  the  worm  about  its  middle,  cut  it  in  half  witff 
its  forcepts,  and  preyed  upon  one  part,  while  the  other  efcaped.  ^ 
Which  evinces  they  have  defign  in  flopping  the  mouths  of  ] 
their  habitations. 

4.  Thewafpof  this  country  fixes  hishabitation  under  ground, 
that  he  may  not  be  affedfed  with  the  various  changes  of  our  cli- 
mate ; but  in  Jamaica  he  hangs  it  on  the  bough  of  a tree,  where 
the  feafons  are  lefs  fevere.  He  weaves  a very  curious  paper  of 
vegetable  fibres  to  cover  his  neft,  which  is  conftrudfed  on  the 
fame  principle  with  that  of  the  bee,  but  with  a different  mate- 
rial ; but  as  his  prey  confifts  of  fieflr,  fruits,  and  infedts,  which 
are  perifhable  commodities,  he  can  lay  up  no  provender  for  the 
winter. 

M.  de  I/Oubiere,  in  his  relatien  of  Siam,  fays,  “ That  in  a 
part  of  that  kingdom,  which  lies  open  to  great  inundations,  all 
the  ants  make  their  fettlements  upon  trees ; no  ants’  nefts  are  to 
be  feen  any  where  elfe  ;”  whereas,  in  our  country,  the  ground 
is  their  only  fituation.  From  the  fcriptural  account  of  thefe  in- 
fects, one  might  be  led  to  fulpect,  that  in  tome  climates  thev  lav 
up  a provifion  for  the  winter,  Origen  affirms  the  fame ; (Cont. 
Celf.  L.  4.)  but  it  is  generally  believed  that  in  this  countrv 
they  do  not.  (Prov.  vi.  6.  xxx.  25.)  The  white  ants  of  the  coaft 
of  Africa  make  themfelves  pyramids,  eight  or  ten  feet  high,  on  a 
bale  of  about  the  fame  width,  with  a ffnooth  furface  of  rich  clav- 
exceflively  hard  and  well  built,  which  appear  at  a difiance  like 

an  . 


OF  INSTINCT. 


Sect.  X-VI.  17. 


m 


an  affemblage  of  the  huts  of  the  negroes.  (Adanfon.)  Thehif- 
tory  of  thel'e  has  been  lately  well  described  in  the  Philofoph. 
Tranfacftions,  under  the  name  of  termes,  or  termites.  Thefe 
differ  very  much  from  the  nefts  of  our  large  ant ; but  the  real 
hiftory  of  this  creature,  as  well  as  of  the  wafp,  is  yet  very  im- 
pcrfedbly  known. 

Wafps  are  laid  to  catch  large  fpiders,  and  to  cut  off  their 
legs,  and  carry  their  mutilated  bodies  to  their  young.  (Did. 
Raifon,  Tom.  1.  p.  152.) 

One  circumftance  I shall  rela-te  which  fell  under  my  own 
.eye,  and  (hewed  the  power  of  reafon  in  a wafp,  as  it  is  exer- 
clfed  among  men.  A wafp,  on  a gravel  walk,  had  caughfa 
fly  nearly  as  large  as  himfelf ; kneeling  on  the  ground,  I ob- 
ferved him  feparate  the  tail  and  the  head  from  the  body  part, 
to  which  the  wings  were  attached.  He  then  took  the  body- 
part  in  his  paws,  and  rofe  about  two  feet  from  the  ground  with 
jt ; but  a gentle  breeze  wafting  the  wings  of  the  fly,  turned 
him  round  in  the  ah,  and  he  fettled  again  with  his  prey  upon 
the  gravel.  I then  diftinctly  obferved  him  cut  off  with  his 
mouth,  firft  one  of  the  wings,  and  then  the  other,  after  which 
he  flew  away  with  it  unmole  fled  by  the  wind. 

Go,  thou  fluggard,  learn  arts  and  induftry  from  the  bee, 
sand  from  the  ant ! 

Go,  proud  reafoner,  and  call  the  worm  thy  After ! 

XVII.  ' Conclujion . 

It  was  before  obferved  how  much  the  fuperior  accuracy  of 
our  fenfe  of  touch  contributes  to  increafe  our  knowledge  ; but 
it  is  the  greater  energy  and  activity  of  the  power  of  volition 
(as  explained  in  the  former  Sedtions  of  this  work)  that  marks 
mankind,  and  has  given  him  the  empire  of  the  world. 

There  is  a criterion  by  which  we  may  diftinguifh  our  vo- 
luntary acts  or  thoughts  from  thofe  that  are  excited  by  ourfen- 
fations.  “ The  former  are  always  employed  about  the  means 
to  acquire  pleafureable  objecfts,  or  to  avoid  painful  ones : 
while  the  latter  are  employed  about  the  pojftjjion  of  thofe  that 
are  already  in  our  power.” 

If  we  turn  our  eyes  upon  the  fabric  of  our  fellow  animals, 
we  find  they  are  fupported  with  bones,  covered  with  fkins, 
moved  by  mufcles  ; that  they  poffefs  the  fame  fenfes,  acknow- 
ledge the  fame  appetites,  and  are  nourifhed  by  the  fame  ali- 
ment with  ourfelves ; and  we  fhould  hence  conclude,  from  the 
{irongeft  analogy,  that  their  internal  faculties  were  alfo  in 
tome  meafure  fimilar  to  our  own. 

Mr,  Lock  indeed  publiftied  an  opinion,  that  other  animals 

pofleffcd 


134  CATENATION  OF  MOTIONS.  Sect.  XVII.  i. 

poflcffed  no  abftradf  or  general  ideas,  and  thought  this  circum-  ^ 
fiance  was  the  barrier  between  the  brute  and  the  human  world.  '% 
But  thefe  abftradted  ideas  have  been  fmcedemonftrated  by  bilhop 
Berkley,  and  allowed  by  Mr.  Hume,  to  have  no  exigence  in  j 
nature,  not  even  in  the  mind  of  their  inventor,  and  we  are  hence 
neceffitated  to  look  for  lome  other  mark  of  diftindlion. 

The  ideas  and  adtions  of  brutes,  like  thofe  of  children,  are 
almoft  perpetually  produced  by  their  prefent  pleafures,  or  their 
prelent  pains ; and,  except  in  the  few  inftances  that  have  been 
mentioned  in  this  Sedfion,  thay  leldom  bufy  themfelves  about  the 
means  of  procuring  future  blifs,  or  of  avoiding  future  miiery.  I 
Whilft  the  acquiring  of  languages,  the  making  of  tools,  and 
the  labouring  for  money,  which  are  all  only  the  means  of  pro- 
curing pleafure ; and  the  praying  to  the  Deity,  as  another  means 
to  procure  happinefs,  are  charadteriftic  of  human  nature. 


SECT.  XVII. 

THE  CATENATION  OF  MOTIONS. 

I.  i.  Catenations  of  animal  motion.  2.  Are  produced  by 
irritations , by  fenfations , by  volitions.  3.  They  continue  - 
,fome  time  after  they  have  been  excited.  Caufe  of  cate~  4 
nation.  4.  JVe  can  then  exert  our  attention  on  ether  ob-  j 
jeds.  5.  Many  catenations  of  motions  go  on  together,  j 
6.  Some  links  of  the  catenations  of  motions  may  be  left  out  •( 
without  difuniting  the  chain.  7.  Interrupted  circles  of 
motion  continue  confufedly  till  they  come  to  the  part  of  the  • 
circle  where  they  were  difurbed.  8.  IVeakcr  catena- 
tions are  diffevered  by  fronger.  9.  Then  new  catena- 
tions take  place.  xo.  Much  effort  prevents  their  re-unit- 
ing. Impediment  of  f beech.  11.  Trams  more  eafly  dif- 

fevered than  circles.  12.  Sleep  defroys  volition  and  ex- 
ternal fiimulus.  II.  Infanccs  of  Various  catenations  in 
a young  lady  playing  on  the  harpf chord.  III.  1.  I That 
catenations  are  the  Jlrongcf.  2.  Irritations  joined  with 
afociations  form  jlrongejl  connexions.  Vital  motions. 

3.  New  links  with  incrcafcd  force  ; cold fits  of  fever  pro- 
duced. 4.  New  links  with  decreafed force.  Cold  bath. 

5.  Irritation  joined  with  fenjation.  Inflammatory  fever. 
IVhy  children  cannot  tickle  themfelves.  6.  Volition  join- 
ed with  fenfation.  Irritative  ideas  of  found  become  Jen- 
fible.  7.  Ideas  of  imagination  dijjcvercd  by  irritations , 
by  volition,  production  of  furprife. 

I.  1.  TO  inveftigate  with  precilion  the  catenations  of  ani- 
mal motions,  it  would  be  well  to  attend  to  the  manner  of  their 

produdlionj 


Sect.  XVII.  i.  CATENATION  OF  MOTIONS.  135 

production  ; but  we  cannot  begin  this  difquifition  early  enough 
for  this  purpofe,  as  the  catenations  of  motion  feem  to  begin 
with  life,  and  are  only  extingufhable  with  it.  "W e have  fpo- 
l^en  of  the  power  of  irritation,  of  fenfation,  of  volition,  and  of 
affociation,  as  preceding  the  fibrous  motions  ; we  now  ftep 
forwards,  and  conlider,  that  converfely  they  aie,  in  their  turn, 
preceded  by  thofe  motions ; and  that  all  the  fucceflive  trains 
or  circles  of  our  actions  are  compofed  of  this  two-fold  concate- 
nation. Thofe  we  fhall  call  trains  of  addion,  which  continue 
to  proceed  without  any  ftated  repetitions ; and  thofe  circles  of 
action,  when  the  parts  of  them  return  at  certain  periods,  though 
the  trains  of  which  they  confift  are  not  exadbly  fimilar.  The 
reading  an  epic  poein  is  a train  of  actions ; the  reading  a fong, 
with  a chorus  at  equal  diftances  in  the  meafure,  conftitutes  lo 
many  circles  pf  addion. 

2.  Some,  catenations  of  animal  motion  are  produced  by  rei- 
terated fucceflive  irritations,  as  when  we  learn  to  repeat  the 
alphabet  in  its  order,  by  frequently  reading  the  letters  of  it. 
Thus,  the  vermicular  motions  of  the  bowels  were  originally 
pr  duced  by  the  fucceflive  irritations  of  the' palling  aliment ; 
and  the  fuccefllon  of  adbions  of  the  auricles  and  ventricles  of 
the  heart,  was  originally  formed  by  fucceflive  ftimulus  of 
the  blood  ; thefe  afterwards  become  part  of  the  diurnal  circles 
of  animal  addions,  as  appears  by  the  periodical  returns  of  hun- 
ger, and  the  quickened  pulfe  of  weak  people  in  the  evening. 

Other  catenations  of  animal  motion  are  gradually  acquired 
by  fucceflive  agreeable  fenfations,  as  in  learning  a favourite 
fong  or  dance ; others  by  difagreeable  fenfations,  as  in  coughing 
or  nidbitation ; thefe  become  aflociated  by  frequent  repetition, 
and  afterwards  compofe  parts  of  greater  circles  of  addion,  like 
thofe  above-mentioned.  ’ 

Other  catenations  of  motions  are  gradually  acquired  by  fre- 
quent voluntary  repetitions ; as  when  we  deliberately  learn  to 
march,  read,  fence,  or  any  mechanic  art,  the  motions  of  many 
of  our  mufcles  become  gradually  linked  together  in  trains,  tribes, 
or  circles  of  addion.  Thus,  when  any  one  at  firft  begins  to 
ufe  the  tools  in  turning  wood  or  metals  in  a lathe,  he  wills  the 
motions  of  his  hand  or  fingers,  till  at  length  thefe  addions  be- 
come fo  connedded  with  the  effedb,  that  he  feems  only  to  will  the 
point  of  the  chiffel.  Thefe  are  caufed  by  volition,  connedded  by 
affociation,  like  thofe  above  defcribed,  and  afterwards  become 
parts  of  ourdiurnal  trains  or  circles  of  addion. 

3.  All  thefe  catenations  of  animal  motions  are  liable  to  pro- 
ceed fome  time  after  they  are  excited,  unlefs  they  are  difturbed 
9?  impeded  by  other  irritations,  fenfations,  or  volitions ; and  in. 

many 


13.6  CATENATION  OF  MOTIONS.  Sect.  XVII.  r. 

many  inflances  in  fpite  of  our  endeavours  to  flop  diem;  and 
this  property  of  animal  motions  is  probably  the  caufe  of  their 
catenation.  Thus,  when  a child  revolves  forne  minuses  on  one 
foot,  the  fpedtra  of  the  ambient  objects  appear  to  circulate 
round  him  fome  time  Sifter  he  falls  upon  the  ground.  Thus  the 
palpitation  of  the  heart  continues  fome  time  after  the  object  of 
fear,  which  occafioned  it,  is  removed.  The  biufli  of  fhame, 
which  is  an  excefs  of'fenfati on,  and  the  glow  of  anger,  which 
Is  an  excefs  ot  volition,  continue  fome  time,  though  the  a:- 
fedted  perfon  finds  that  thofe  emotions  were  caufed  by  mif- 
taken  fadts,  and  endeavours  to  extinguifh  their  appearance. 
See  Sedt.  XII.  I.  5. 

4.  When  a circle  of  motions  becomes  connected  bv  fre- 
quent repetitions  as  above,  we  can  exert  our  attention  ftrongiv 
on  other  objedts,  and  the  concatenated  circle  of  motions  will 
neverthelefs  proceed  in  due  order  , as  whilft  you  are  thinking 
on  this  fubjedt,  you  ufe  variety  of  mufcles  in  walking  about 
your  parlour,  or  in  fitting  at  ypur  writing-table. 

5.  Innumerable  catenations  of  motions  may  proceed  at  the 
fame  time,  without  incommoding  each  other.  Of  thefe  are 
the  motions  of  the  heart  and  arteries ; thofe  , of  digeftion  and 
glandular  fecretlon  ; of  the  ideas,  or  fenfual  motions ; thofe 
of  progreflion,  and  of  fpeaking;  the  great  annual  circle  of 
adtions,  fo  apparent  in  birds  in  their  times  of  breeding  and 
moulting;  the  monthly  circles  of  many  female  animals , and  the 
diurnal  circles  of  fleeping  and  waking,  of  fulnefs  and  inanition. 

6.  Some  links  of  fucceffive  trains,  or  of  fynchronous  tribes 
of  adtion,  may  be  left  out  without  disjoining  the  whole.  Such 
are  our  ufual  trains  of  recolledtion ; after  having  travelled 
through  an  entertaining  country,  and  viewed  many  delightful 
lawns,  rolling  rivers,  and  echoing  rocks  ; in  the  recolledtion  of 
our  journev,  we  leave  out  the  many  diftridts  that  we  eroded 
which  were  marked  with  no  peculiar  pleaiure.  Such  alfo  are 
our  complex  ideas  ; they  are  catenated  tribes  of  ideas,  w hich  do 
not  perfedtly  referable  their  correfpondent  perceptions,  becaule 
feme  of  the  parts  are  omitted. 

7.  If  an  interrupted  circle  of  adtions  is  not  entirely  difTever- 
ed,  it  will  continue  to  proceed  confufedly,  till  it  comes  to  the 
part  of  the  circle  where  it  was  interrupted. 

The  vital  motions  in  a fever  from  drunkennefs,  and  in  other 
periodical  difeafes,  are  inflances  of  this  circumftance.  Tire 
accidental  inebriate  does  not  difeover  himfelf  perfedflv  till  about 
the  fame  hour  on  the  fucceeding  day.  The  accuftcvned  drunk- 
ard is  difordered,  it  he  has  not  his  ufual  potation  ot  fermented 
liquor.  So,  if  a confiderable  part  of  a connected  tribe  of  adtion 
- 'be 


Sect.  XVII.  i.  CATENATION  OF  MOTIONS,  i p 

be  difturbed,  that  whole  tribe  goes  on  with  confufion,  till  the 
part  of  the  tribe  affected  regains  its  accuftorned  catenations'. 
So  vertigo  produces  vomiting,  and  a great  fecretion  of  bile, 
as  in  fea-ficknefs,  all  thefe  being  parts  of  the  tribe  of  irritative 
catenations. 

8.  Weaker  catenated  trains  may  be  diffevered  by  the  fodders 
exertion  of  the  ftronger.  When  a child  firft  attempts  to  walk 
acrols  a room,  call  to  him  and  he  inftantly  falls  upon  the  ground. 
So,  while  I am  thinking  over  the  virtues  of  my  friends,  if  the  tea- 
kettle fpurt  out  forne  hot  water  on  my  flocking,  the  fudden 
pain  breaks  the  weaker  chain  of  ideas,  and  introduces  a new 
group  of  figures  of  its  own.  This  circumflance  is  extended  to 
fome  unnatural  trains  of  adtion,  which  have  not  been  confirm- 
ed bv  long  habit ; as  the  hiccough,  or  an  ague-fit,  which  arc 
frequently  curable  by  furprife.  A young  lady,  about  eleven 
years  old,  had,  for  five  days,  a contradtion  of  one  mufcle  in 
her  fore-arm,  and  another  in  her  arm,  which  occurred  four 
or  five  times  every  minute  ; the  mufcles  were  feen  to  leap,  but 
without  bending  the  arm.  To  counteract  this  new  morbid  ha- 
bit an  iffue  was  placed  over  the  convulfed  mufcle  of  her  arm, 
and  an  adhefive  plafler,  wrapped  tight  like  a bandage  over  the 
whole  fore-arm,  by  which  the  new  motions  were  immediately 
deflroyed,  but  the  means  were  continued  fome  weeks  to  pre- 
vent a return. 

9.  It  any  circle  of  adtions  is  diffevered,  either  by  omiffion 
of  fome  of  the  links,  as  in  fleep,  or  by  infertion  of  other  links, 
as  in  furprife,  new  catenations  take  place  in  a greater  or  lefs  de- 
gree. The  lafl  link  of  the  broken  chain  of  adtions  becomes 
connected  with  the  new  motion  which  has  broken  it,  or  with 
that  which  was  neareft  the  link  omitted;  and  thefe  new  cate- 
nations proceed  inftead  of  the  old  ones.  Hence  the  periodic  re- 
turns of  ague-fits,  and  the  chimeras  of  our  dreams. 

10.  Ifa  train  of  adtions  is  diffevered,  much  effort  of  volition 
or  fenfation  will  prevent  its  being  reftored.  Thus,  in  the  com- 
mon impediment  of  fpeech,  when  the  affociation  of  the  motions 
of  the  mufcles  of  enunciation  with  the  idea  of  die  word  to  be 
fpoken  is  difordered,  the  great  voluntary  efforts,  which  diftort 
the  countenance,  prevent  the  rejoining  of  the  broken  affocia- 
tions.  See  No.  II.  10.  of  this  Section.  It  is  thus  likevyife  ob- 
fervable  in  fome  inflammations  of  the  bowels,  the  too  ftrong  ef- 
forts made  by  the  nrulcles  to  carry  forwards  the  offending  ma- 
terial fixes  itmore  firmly  in  its  place,  and  prevents  the  cure. — 
So,  in  endeavouring  to  recall  to  our  memory  fome  particular 
word  of  a fentence,  if  we  exert  ourfelves  too  firongly  about  it, 
we  are  lefs  likely  to  regain  it. 


11.  Catenate^ 


i3S  CATENATION  OF  MOTIONS.  Sect.  XVII.  2. 

11.  Catenated  trains  or  tribes  of  action  are  eafier  diffevered 
than  catenated  circles  of  adtion.  Hence  in  epileptic  fits  the  iyn- 
chronous  connedted  tribes  of  adtion,  which  keep  the  body 
eredt,  are  diffevered,  but  the  circle  of  vital  '.notions  continues 
tmdiflurbed. 

12.  Sleep  deftroys  the  power  of  volition,  and  precludes  the 
ftimuli  of  external  objects,  and  thence  diffcvers  the  trains,  of 
which  thefe  are  a part ; which  confirms  the  other  catenations, 
as  thofe  of  the  vital  motions,  fecretions,  and  absorptions ; and 
produces  the  new  trains  of  ideas,  which  conflitute  our  dreams. 

II.  1.  All  the  preceding  circumflatices  of  the  catenations 
of  animal  motions,  will  be  more  clearly  underflood  by  the  fol- 
lowing example  of  a perfon  learning  mufic ; and  when  we  re- 
coiled! the  variety  of  mechanic  arts,  which  are  performed  by 
aiiociated  trains  of  mufcular  adlions,  catenated  with  the  effedts 
they  produce,  as  in  knitting,  netting,  weaving;  and  the  greater 
variety  of  affociated  trains  of  ideas  caufed,  or  catenated  by  vo- 
litions, or  fenfations,  as  in  our  hourly  modes  of  reafoning,  or 
imagining,  or  recolledting,  we  fhall  gain  fome  idea  of  the  innu- 
merable catenated  trains  and  circles  of  adlion,  which  ferm  the 
tenor 'of  our  lives,  and  which  began,  and  will  only  ceafe  en- 
tirely with  them. 

2.  When  a young  lady  begins  to  learn  mufic,  fhe  voluntarily 
applies  herfelf  to  the  charadlers  of  her  mulic-book,  and  by  ma- 
ny repetitions  endeavours  to  catenate  them  with  the  proportions 
of  found,  of  which  they  arefymbols.  The  ideas  excited  by  the 
mufical  charadlers  are  flowly  connected  with  the  keys  of  the 
harpfichord,  and  much  effort  is  neceffary  to  produce  every  note 
with  the  proper  finger,  and  in  its  due  place  and  time;  till  at 
length  a train  of  voluntary  exertions  becomes  catenated  with 
certain  irritations.  As  the  various  notes,  by  frequent  repei itions, 
become  connected  in  the  order  in  which  they  are  produced,  a 
new  catenation  of  fenfitive  exertions  becomes  mixed  with  the 
voluntary  ones  above  defcribed ; and  not  only  the  mufical  tym- 
bols  of  crotchets  and  quavers,  but  the  auditory  notes  and  tones, 
at  the  fame  time,  become  fo  many  fucceflive  or  fvnchronous 
links  in  this  circle  of  catenated  adlions. 

At  length  the  motions  of  her  fingers  become  catenated  with 
the  mufical  charadlers ; and  thefeno  fooner  flrike  the  eye  titan 
the  finger  preffes  down  the  key  without  any  voluntary  atten- 
tion between  them:  the  adlivity  of  the  hand  being  connedled 
with  the  irritation  of  the  figure,  or  place  of  the  mufical  lyntbol 
on  the  retina;  till  at  length,  by  frequent  repetitions  of  the  lame 
tune,  the  movements  of  her  fingers  in  playing,  and  the  muicles 
of  the  Larynx  in  tinging,  become  affociated  with,  each  ether,  and 

form 


Sect.  XVII.  2.  CATENATION  OF  MOTIONS.  139 

form  part  of  thofe  intricate  trains  and  circles  of  catenated  mo- 
tions, according  with  the  fecond  article  of  the  preceding  propo- 
rtions in  No.  1.  of  this  Sedfion. 

3.  Befides  the  facility,  which,  by  habit,  attends  the  execution  of 
this  mufical  perfomance,  a curious  circumftance  occurs,  which 
is,  that  when  our  young  mufician  has  began  a tune,  {he  finds 
herfelf  inclined  to  continue  it,  and  that  even  when  fhe  is  care- 
lefsly  finging  alone,  without  attending  to  her  own  fong,  accord- 
ing with  the  third  preceding  article. 

4.  At  the  fame  time  that  our  young  performer  continues  to 
play  with  great  exadfnefs  this  accuftomed  tune,  fhe  can  bend 
her  mind,  and  that  intenfely,  on  fome  other  object,  according 
with  the  fourth  article  of  the  preceding  propofitions. 

The  manufcript  copy  of  this  work  was  lent  to  many  of 
my  friends,  at  different  times,  for  the  purpofe  of  gaining  their 
opinions  and  criticifms  on  many  parts  of  it,  and  I found  the 
following  anecdote  written  with  a pencil  oppofite  to  this  page, 
but  am  not  certain  by  whom : “ I remember  feeing  the  pretty 
young  adtrefs,  who  fucceeded  Mrs.  Arne  in  the  performance 
of  the  celebrated  Padlock,  rehearfe  the  mufical  parts  at  her 
harpfichord,  under  the  eye  of  her  mafter,  with  great  tafte  and 
accuracy,  though  I obferved  her  countenance  full  of  emotion, 
which  I could  not  account  for  ; at  laft  fhe  fuddenly  burft  into 
tears ; for  fhe  had  all  this  time  been  eyeing  a beloved  Canary 
bird  fuffering  great  agonies,  which  at  that  inftant  fell  dead 
from  its  perch.” 

5.  At  the  fame  time  many  other  catenated  circles  of  adlion 
are  going  on  in  the  perfon  of  our  fair  mufician,  as  well  as  the 
motions  of  her  fingers,  fuch  as  the  vital  motions,  refpiration, 
the  movements  of  her  eyes  and  eyelids,  and  of  the  intricate 
mufcles  of  vocality,  according  with  the  fifth  preceding  article; 

6.  If  by  any  ftrong  impreffion  on  the  mind  of  our  fair  mu- 
fician, fhe  fhould  be  interrupted  for  a very  inconfiderable  time, 
fhe  can  ftill  continue  her  performance,  according  to  dieJjxth 
article. 

7.  If,  however,  this  interruption  be  greater,  though  the  chain 
of  adtions  be  not  diftevered,  it  proceeds  confufedly,  and  our 
young  performer  continues  indeed  to  play,  but  in  a hurry,  with- 
out accuracy  and  elegance,  till  fhe  begins  the  tune  again,  ac- 
cording to  the  feventh  of  the  preceding  articles. 

8.  But  if  this  interruption  be  ftill  greater,  the  circle  of  ac« 
tions  becomes  entirely  diftevered,  and  fhe  finds  herfelf  imme- 
diately under  the  neceflity  to  begin  over  again  to  recover  the 
loft  catenation,  according  to  the  eighth  preceding  article. 

9.  Or,  in  trying  to  recover  it,  fhe  will  ling  fome  diffonant 

U notes. 


i4o  CATENATION  OF  MOTIONS.  Sect.  XVII.  2. 

notes,  or  ftrike  fome  improper  keys,  according  to  the  ninth 
preceding  article. 

10.  A very  remarkable  thing  attends  this  breach  of  catena- 
tion: if  the  performer  has  forgotten  fome  word  of  her  fong,  the 
mere  energy  of  mind  fhe  ules  about  it,  the  more  diftant  is  fhe 
from  regaining  it;  and  artfully  employs  her  mind,  in  part,  on 
fome  other  objedt,  or  endeavours  to  duli  its  perceptions,  con- 
tinuing to  repeat,  as  it  were  inconfcioufly,  the  former  part  of 
the  fong,  that  fire  remembers,  in  hopes  to  regain  the  loft  con- 
nedlion. 

For  if  the  activity  of  the  mind  itfelf  be  more  energetic,  or 
takes  its  attention  more,  than  the  connedling  word,  which  i* 
wanted,  it  will  not  perceive  the  flighter  link  of  this  loft  word-* 
as  who  liftens  to  a feeble  found,  muft  be  very  ftlent  and  motion- 
lefs  ; fo  that  in  this  cafe  the  very  vigour  of  the  mind  itfelf  feems 
to  prevent  it  from  regaining  the  loft  catenation,  as  well  as  the 
too  great  exertion  in  endeavouring  to  regain  it,  according  to 
the  tenth  preceding  article. 

We  ftequently  experience,  when  we  are  doubtful  about  the 
fpelling  of  a word,  that  the  greater  voluntary  exertion  we  ufe, 
thac  is,  the  more  intenfely  we  think.about  it,  the  further  are  we 
from  regaining  the  loft  affociation  between,  the  letters  of  it,  but 
which  readily  recurs  when  we  have  become  careleis  about  it. 
In  the  fame  manner,  after  having  for  an  hour  laboured  to  recol- 
lect the  name-  of  fome  abfent  perfon,  it  {hall  feem,  particularly 
after  fleep,  to  come  into  the  mind  as  it  were  fpontaneoufly ; that 
is,  the  word  we  are  in  fearch  of,  was  joined  to  the  preceding  one 
by  aflfociation ; this  aflociation  being  diflfevered,  we  endeavour 
to  recover  it  by  volition ; this  very  adtion  of  the  mind  fti  ikes 
our  attention  more  than  the  faint  link  of  aflcciation,  and  we 
find  it  impoflible,  by  this  means,  to  retrieve  the  loft  word.  After 
fleep,  when  volition  is  entirely  fufpended,  the  mind  becomes 
capable  of  perceiving  the  fainter  link  of  aflociation,  and  the 
word  is  regained. 

On  this  circumftance  depends  the  impediment  of  fpeech  be- 
fore mentioned ; the  ftrft  fy  liable  of  a word  is  caufable  by  voli- 
tion, but  the  remainder  of  it  is,  in  common  converfation,  intro- 
duced by  its  affociations  with  this  ftrft  fyllable,  acquired  by  long 
habit.  Hence,  when  the  mind  of  die  ftammerer  is  vehemendy 
employed  on  fome  idea  or  ambition  of  Alining,  or  fear  of  not 
fucceeding,  the  aflfociations  of  the  motions  of  the  mufcles  of  ar- 
ticulation with  each  other  become  diflevered  by  this  greater  ex- 
ertion, and  he  endeavours,  in  vain,  by  voluntary  efforts,  to  rejoin 
the  broken  aflociation.  For  this  purpofe  he  continues  to  repeat 
the  ftrft  fyllable,  which  is  caufable  by  volition,  and  drives  in  vain. 


Sect.  XVII.  3.  CATENATION  OF  MOTIONS.  141 

by  various  diftortions  of  countenance,  to  produce  the  next  links 
which  are  fubjeX  to  affociation.  See  Clals  IV.  3.  1.  1. 

11.  After  our  accomplifhed  mufician  has  acquired  great  va- 
riety of  tunes  and  fongs,  fo  that  iome  of  them  begin  to  ceafe  to 
be  eafily  recollected,  fhe  finds  progreffive  trains  of  mufical  notes 
more  frequently  forgotten  than  thofe  which  are  compofed  of 
reiterated  circles,  according  with  the  eleventh  preceding  article. 

12.  To  finifh  our  example  with  the  preceding  articles,  we 
mult  at  length  fuppofe,  that  our  fair  performer  falls  afleep  over 
her  harpfichord ; and  thus,  by  the  fuipenlion  of  volition,  and 
the  exclufion  of  external  ftimuli,  fhe  diffevers  the  trains  and 
circles  of  her  mufical  exertions. 

III.  1.  Many  of  thele  circumftances  of  catenations  of  mo- 
tions receive  an  eafy  explanation  from  the  four  following  con- 
fequences  to  the  feventh  law  of  animal  cauiation  in  SeCt.  IV. 
Thele  are,  firlt,  that  thofe  fucceffions  or  combinations  of  ani- 
mal motions,  whether  they  were  united  by  caufation,  affocia- 
tion,  or  catenation,  which  have  been  mojft  frequently  repeated, 
acquire  the  ftrongeft  connexion.  Secondly,  that  or  thefe,  thofe 
which  have  been  lefs  frequently  mixed  with  other  trains  or  tribes 
of  motion,  have  the  ftrongeft  connexion.  Thirdly,  that  of 
thefe,  thofe  which  were  firft  formed,  have  the  ftrongeft  con- 
nexion. Fourthly,  that  if  an  animal  motion  be  excited  by 
more  than  one  caufation,  affociation,  or  catenation,  at  the 
fame  time,  it  will  be  performed  with  greater  energy. 

2.  Hence  alfo  we  underftand  why  the  catenations  of  irri- 
tative motions  are  more  ftrongly  conneXed  than  thofe  of 
the  other  claffes,  where  the  quantity  of  unmixed  repetition 
has  been  equal;  becaufe  they  were  firft  formed.  Such  are 
thofe  of  the  feccrning  and  abforbent  fyftems  of  veffels,  where 
the  aXion  of  the  gland  produces  a fluid,  which  ftimulates  the 
mouths  of  its  correfpondent  abforbents.  The  affociated  mo- 
tions feem  to  be  the  next  mod  ftrongly  united,  from  their  fre- 
quent repetition ; and  where  both  thefe  circumftances  unite, 
as  in  the  vital  motions,  their  catenations  are  indiffoluble,  but 
by  the  deftruXion  of  the  animal. 

3.  Where  a new  link  has  been  introduced  into  a circle  of 
aXions  by  fome  accidental  defeX  of  ftimulus ; if  that  defeX  of 
ftimulus  be  repeated  at  the  fame  part  of  the  circle  a fecond  or  a 
third  time,  the  defeXive  motions  thus  produced,  both  by  the  re- 
peated defeX  of  ftimulus  and  by  their  catenation  with  the  parts 
of  the  circle  of  aXions,  will  be  performed  with  lefs  and  lefs  ener- 
gy. Thus  if  any  perfon  is  expeled  to  cold  at  a certain  hour  to- 
day, fo  long  as  to  render  fome  part  of  the  fyftem  for  a time  tor- 
pid, and  is  again  expofed  to  it  at  the  fame  hour  to-morrow,  and 

the 


142  CATENATION  OF  MOTIONS.  Sect.  XVII.  3. 

the  next  day,  he  will  be  more  and  more  affedted  by  it,  till 
at  length  a cold  fit  of  fever  is  completely  formed,  as  happens  at 
the  beginning  of  many  of  thofe  fevers  which  are  called  nervous 
or  low  fevers ; where  the  patient  has  flight  periodical  fhiver- 
ings  and  palenefs  for  many  days  before  the  febrile  paroxyfm  is 
completely  formed. 

4.  On  the  contrary,  if  the  expofure  to  cold  be  for  fo  fhort 
a time  as  not  to  induce  any  confiderable  degree  of  torpor  or 
quiefcence,  and  is  repeated  daily  as  above-mentioned,  it  lol'es  its 
efFedb  more  and  more  at  every  repetition,  till  the  conftitution 
can  bear  it  without  inconvenience,  or  indeed  without  being 
confcious  of  it ; as  in  walking  into  coid  air  in  frofty  weather. 
The  fame  rule  is  applicable  to  increafed  flimulus,  as  of  heat, 
or  or  vinous  fpirit,  within  certain  limits,  as  is  applied  in  the 
two  lafl:  paragraphs  to  Deficient  Stimulus,  as  is  further  ex- 
plained in  Sedl.  XXXVI.  on  the  Periods  of  Difeafes. 

5.  Where  irritation  coincides  with  fenfation  to  produce 
the  fame  catenations  of  motion,  as  in  inflammatory  fevers, 
they  are  excited  with  ftiil  greater  energy  than  by  the  irrita- 
tion alone.  So,  when  children  expedl  to  be  tickled  in  play, 
by  a feather  lightly  pafled  over  the  lips,  or  by  gently  vellicat- 
ing  the  foies  of  their  feet,  laughter  is  mod  vehemently  excit- 
ed ; though  they  can  ftimulate  thefe  parts  with  their  own  fin- 
gers unmoved.  Here  the  pleafureable  idea  of  playfulnefs  coin- 
cides with  the  vellication ; and  there  is  no  voluntary  exertion 
ufed  to  diminifh  the  fenfation,  as  there  would  be  if  a child 
fhould  endeavour  to  tickle  himfelf.  See  Seft.  XXXIV.  1.  4. 

6.  And,  laftly,  the  motions  excited-  by  the  junclion  of  vo- 
luntary exertion  with  irritation,  are  performed  with  more  ener- 
gy than  thofe  by  irritation  fingly ; as  when  we  liften  to  fmall 
noifes,  as  to  the  ticking  of  a watch  in  the  night,  we  perceive 
the  moft  wreak  founds,  that  are  at  other  times  unheeded.  So, 
when  we  attend  to  the  irritative  ideas  of  found  in  our  ears, 
which  are  generally  not  attended  to,  w-e  can  hear  them ; and 
can  fee  the  Ipefilra  of  objects,  which  remain  in  the  eye,  when- 
ever we  pleafe  to  exert  our  voluntary  power  in  aid  of  thofe 
weak  actions  of  the  retina,  or  of  the  auditory  nerve. 

7.  The  temporary  catenations  of  ideas,  which  are  caufed 
by  the  fenfations  of  pleafure  or  pain,  are  eafilv  diflevered  either 
by  irritations,  as  when  a fudden  noife  dilturbs  a day-dream  ; or 
by  the  power  of  volition,  as  when  we  awake  from  fleep.  Hence, 
in  our  waking  hours,  whenever  an  idea  occurs,  which  is  in- 
congruous to  our  former  experience,  we  inftantly  diflever  the 
train  of  imagination  by  the  power  of  volition,  and  compare 
the  incongruous  idea  with  our  previous  knowledge  of  nature, 


Sect.  XVIII. 


OF  SLEEP. 


*43 

and  rejedt  it.  This  operation  of  the  mind  has  not  yet  acquir- 
ed a fpecific  name,  though  it  is  exerted  every  minute  of  our 
waking  hours ; unlefs  it  may  be  termed  intuitive  ana- 
logy. It  is  an  add  of  reafoning,  of  which  we  are  unconfci- 
ous,  except  from  its  effedfs  in  preferving  the  congruity  of  our 
ideas,  and  bears  the  fame  relation  to  the  fenforial  power  of  vo- 
lition, that  irritative  ideas,  of  which  we  are  inconfcious,  except 
by  their  effedts,  do  to  the  fenforial  power  of  irritation  ; as  the 
former  is  produced  by  volition  without  our  attention  to  it,  and 
the  latter  by  irritation  without  our  attention  to  them. 

If,  on  the  other  hand,  a train  of  imagination  or  of  voluntary 
ideas  are  excited  with  great  energy,  and  paffing  on  with  great 
vivacity,  and  become  dilfevered  by  fome  violent  ftimulus,  as  the 
difcharge  of  a piftol  near  one’s  ear,  another  circurnftance  takes 
place,  which  is  termed  surprise;  which,  by  exciting  violent 
irritation,  and  violent  fenfation,  employs,  for  a time,  the  whole 
fenforial  energy,  and  thus  diffevers  the  palling  trains  of  ideas, 
before  the  power  of  volition  has  time  to  compare  them  with  the 
ufual  phenomena  of  nature.  In  this  cafe  fear  is  generally  the 
companion  of  furprife,  and  adds  to  our  embarraffinent,  as  every- 
one experiences,  in  fome  degree,  when  he  hears  a noife  in  the 
dark,  which  he  cannot  inftantly  account  for.  This  catenation 
of  fear,  with  furprife,  is  owing  to  our  perpetual  experience  of 
injuries  from  external  bodies  in  motion,  unlefs  we  are  upon  our 
guard  againft  them.  See  Sedf.  XVIII.  17.  and  XIX.  2. 

Many  other  examples  of  the  catenations  of  animal  motions 
are  explained  in  Sedf.  XXXVI.  on  the  Periods  of  Difeafes. 


SECT.  XVIII, 

OF  SLEEP. 

I.  Volition  is  fufpended  in  fleep.  1.  Scnfation  continues. 
Dreams  prevent  delirium  and  inflammation.  '3.  Night- 
mare. 4.  Ccafelefs  flow  of  ideas  in  dreams.  5.  JVc  feem 
to  receive  them  by  the  fenfes.  Optic  nerve  perfectly  fen- 
flble  in  fleep.  Eyes  lefs  dazzled  after  dreaming  of  viflble 
objedls.  6.  Reverie,  belief . 7.  How  we  diflinguijh  ideas 
from  perceptions.  8.  Variety,  of  feenery  in  dreams,  excel- 
lence of  the  fenfe  of  viflon.  9.  Novelty  of  combination 
in  dreams.  10.  Diflinffnefs  of  imagery  in  dreams.  1 1. 
Rapidity  of  tranfadlion  in  dreams.  12.  Of  meafuring 
time.  Of  dramatic  time  and  place.  Why  a dull  play  in- 
duces fleep,  and  an  interefling  one  reverie.  13.  Confeiouf- 
nejs  of  our  exiflence  and  identity  in  dreams.  14.  How 


144 


OF  SLEEP. 


Sect.  XVIII.  r. 


we  awake  fametime s fuddenly,  fomctimes  frequently.  ig. 

Irritative  modem  continue  in  feep  ; internal  irritations 
are  face  ceded  by  fenfation.  Senjibility  incrcafes  during 
feep,  and  irritability.  Adorning  dreams.  IV hy  epilepfu . 
occur  in  feep.  Ecflacy  of  children.  Cafe  of  convulsions 
in  feep.  Cramp,  why  painful.  Afhma.  Morning fw  eats. 
Increafe  of  heat.  Increafe  of  urine  in  feep.  Why  more 
liable  to  tale  cold  in  feep.  Catarrh  from  thin  night-caps. 
Why  we  fed  chilly  at  the  approach  of  feep , and  at  wak- 
ing in  the  open  air.  16.  Why  the  gout  commences  in  feep . 
Secretions  art  more  copious  in  feep ; young  animals  and 
plants  grow  more  in  feep.  17.  Inconfflency  of  dreams. 
Ah  fence  of  furprife  in  dreams.  18.  Why  we  forget  fome 
dreams  and  not  others.  19.  Sleep-talkers  awake  with 
furprife.  20.  Remote  caufes  of  feep.  Atmofphere  with 
lefs  oxygene.  Comprejfon  of  the  brain  in  fpina  bifida. 
By  whirling  on  an  horizontal  wheel.  By  cold.  21.  Defi- 
nition of  feep. 

I.  THERE  arc  four  f tuitions  of  our  fydem,  which,  iq 
their  moderate  degrees,  are  not  ufually  termed  difeafes,  and  yet 
abound  with  many  very  curious  and  inftrudive  phenomena  , 
thefe  are  Ileep,  reverie,  vertigo,  drunkennefs.  Thefe  we  fliall 
previously  confider,  before  we  Rep  forwards  to  develope  the 
caufes  and  cures  of  difeafes  with  die  modes  of  the  operation  of 
medicines. 

As  all  thofe  trains  and  tribes  of  animal  motion,  which  are 
fubjeded  to  volition,  were  the  laft  that  were  caufed,  their 
connedion  is  weaker  than  that  ol  the  other  dalles;  and  there 
is  a peculiar  circumftance  attending  this  caufation,  which  is, 
that  it  is  entirely  fufpended  during  Ileep ; whilft  the  other  claf- 
fes  of  motion,  which  are  more  immediately  necellary  to  life, 
as  thole  caufed  by  internal  ftimuli,  for  inllance,  the  pulfa- 
tions  of  the  heart  and  arteries,  or  thofe  catenated  with  plea- 
fureable  fenfation,  as  the  powers  ot  digeilion,  continue  to 
Hrengdien  their  habits  without  interruption.  Thus,  though 
man,  in  his  lleeping  Rate,  is  a much  lefs  perfed  animal  than 
in  his  waking  hours  ; and  though  he  confumes  more  than  one 
third  of  his  life  in  this  his  irrational  iituation  ; yet  is  the  wifdom 
of  the  Author  of  nature  manifeft,  even  in  this  feeming  impel  - 
fedion  of  his  work ! 

The  truth  of  this  alTertion,  with  refped  to  the  large  mufcles 
of  the  body,  which  are  concerned  in  locomotion,  is  evi- 
dent ; as  no  one  in  perfed  fanity  walks  about  in  his  deep,  or  * 
performs  any  domeftic  offices ; and  in  refped  to  the  mind,  wc 

never 


OF  SLEEP. 


Sect.  XVIII.  2,  3. 


*45 


never  exercife  our  reafon  or  recollection  la  dreams;  we  may 
fome times  feem  diftradted  between  contending  pafikras,  but 
we  never  compare  their  objects,  or  deliberate  about  the  ac- 
quifltion  of  thofe  objects,  if  our  deep  is  perfecSL  And  though 
many  fynchronous  tribes,  or  fucceflive  train®  of  ideas,  may  re- 
prefent  the  houfes  or  walks  which  have  real  existence,  yet  are 
they  here  introduced  by  their  connection  with  oar  fenfations, 
and  are  in  truth  ideas  of  imagination,  not  of  recohediioo. 

2.  For  our  fenfations  of  pleafu.e  and  pain  are  experienced 
with  great  vivacity  in  our  dreams  ; and  hence,  all  dm  motley 
group  of  ideas,  which  are  caufed  by  them,  called  the  ideas  of 
imagination,  with  their  various  affociated  trains,  are  in  a very 
vivid  manner  added  over  in  the  fenforium;  and  thefe  feme- 
times  call  into  acftion  the  larger  mufcies,  which  have  been 
much  affociated  with  them  ; as  appears  from  the  mattering 
fentences  which  fome  people  utter  in  their  dreams,  and  from 
the  obfcure  barking  of  fleeping  dogs,  and  the  morions  of  their 
feet  and  noftrils. 

This  perpetual  flow  of  the  trains  of  ideas  which  conflitute 
our  dreams,  and  which  are  caufed  by  painful  or  pleafureable 
fenfations,  might,  at  flrft  view,  be  conceived  to  be  an  uicleis  ex- 
penditure of  fenforial  power.  But  it  has  been  (hewn,  that  thofe 
motions  which  are  perpetually  excited,  as  thofe  of  the  arterial 
fyftem  by  the  ftimulus  of  the  blood,  are  attended  by  a great  ac- 
cumulation of  fenforial  power,  after  they  have  been  tor  a time 
fufpended ; as  the  hot-fit  of  fever  is  the  confequence  of  the  cold 
one.  Now,  as  thefe  trains  of  ideas,  caufed  by  fenfation,  are 
perpetually  excited  during  our  waking  hours,  if  they  were  to  be 
fufpended  in  fleep  like  the  voluntary  motions,  (which  are  exerted 
only  by  intervals  during  our  waking  hours)  an  accumulation  of 
fenforial  power  would  follow  ; and  on  our  awaking,  a delirium 
would  fupervene ; fince  thefe  ideas,  caufed  by  fenfation,  would 
be  produced  with  fuch  energy,  that  we  fhouln  miftake  the  trains 
of  imagination  for  ideas  excited  by  irritation;  as  perpetually 
happens  to  people  debilitated  by  fevers  on  their  flrft  awaking ; 
for  in  thefe  fevers  with  debility,  the  general  quantity  of  irritation 
being  diminifhed,  that  of  fenfation  is  increaled.  In  like  manner, 
if  the  adlions  of  the  ftomach,  interlines,  and  various  glands, 
which  are,  perhaps,  in  part  at  leaft,  caufed  by  or  catenated  with 
agreeable  fenfation,  and  which  perpetually  exit!  during  our 
waking  hours,  were,  like  the  voluntary  motions,  fufpended  in 
our  fleep,  the  great  accumulation  of  fenforial  power  which 
would  neceffarily  follow,  would  be  liable  to  excite  inflamma- 
tion in  them. 

3.  When,  by  our  continued  pofture  in  fleep,  fome  uneafy 

fenfations 


14&  OF  SLEEP  Sect.  XVIII.  4, 

fenfations  are  produced,  we  either  gradually  awake  bv  the  ex- 
ertion of  volition,  or  themufcles,  connected  by  habit  with  fuch 
fenfations,  alter  the  pofition  of  tiie  body:  but  where  the  fleep  is 
uncommonly  profound,  and  thofe  uneafy  fenfations  great,  the 
difeafe  called  the  incubus,  or  nightmare,  is  produced.  Here  the 
delire  of  moving  the  body  is  painfully  exerted,  but  the  power 
of  moving  it,  or  volition,  is  incapable  of  adtion,  till  we  awake. 
Many  leis  difagreeable  ftruggles  in  our  dreams,  as  when  we 
within  vain  to  fly  from  terrifying  objects,  conftitute  a (lighter 
degree  of  this  difeafe.  In  awakening  from  the  nightmare,  I 
have  more  than. once  obferved,  that  there  was  no  diforder  in 
my  pulfe ; nor  do  I believe  the  refpiration  is  laborious,  as  fome 
have  affirmed.  It  occurs  to  people  whofe  fleep  is  too  pro- 
found, and  fome  difagreeable  fenfation  exifts,  which,  at  other 
times  would  have  awakened  them,  and  have  thence  prevented 
the  difeafe  of  nightmare ; as  after  great  fatigue  or  hunger,  with 
too  large  a fupper  and"  wine,  which  occaiion  our  fleep  to  be 
uncommonly  profound.  See  No.  14,  of  this  Sedition. 

4.  As  the  larger  mufcles  of  the  body  are  much  more  fre- 
quently excited  by  volition  than  by  lenfation,  they  are  but 
leldom  brought  into  adtion  in  our  fleep : but  the  ideas  of  the 
mind  are,  by  habit,  much  more  frequently  connected  with  fen- 
faticn  than  with  volition;  and  hence  the  ceafelefs  flow  of  our 
ideas  in  dreams.  Every  one’s  experience  will  teach  him  this 
truth,  for  we  all  daily  exert  much  voluntary  muicular  motion  ; 
but  few  of  mankind  can  bear  the  fatigue  of  much  voluntary 
thinking. 

5.  A very  curious  circumflance  attending  thefe  our  fleep: r.g 
imaginations  is,  that  we  feem  to  receive  them  by  the  fenles. 
The  mufcles,  which  are  fubfervient  to  the  external  organs  of 
fenie,  are  connedted  w ith  volition,  and  ceafe  to  adt  in  fleep  ; 
hence  the  eyelids  are  clofed,  and  the  tympanum  of  the  ear  re- 
laxed; and  it  is  probable  a flmilarity  of  voluntary  exertion  may 
be  neceflary  for  the  perceptions  of  the  other  nerves  of  fenfe ; 
for  it  is  oblerved,  that  the  papillae  of  the  tongue  can  be  feen  to 
become  eredled  when  we  attempt  to  tafte  any  thing  extremely 
grateful.  (Kewfon  Exper.  Enquir.  V.  2.  186.  Albini  Annor. 
Acad.  L.  i.  c.  15.)  Add  to  this,  that  the  immediate  organs  of 
fenfe  have  no  objedfs  to  excite  them  in  the  darknefs  and  fiience 
of  the  night;  but  their  nerves  of  fenfe  nevertheieis  continue  to 
poiTefs  their  perfedt  adlivity,  fubfervient  to  all  their  numerous 
leniitive  eonnedtions.  This  vivacity  of  our  nerves  ot  fenie 
during  the  time  of  fleep,  is  evinced  by  a circumflance,  which 
almofr  every  one  muft,  at  fome  time  or  other,  have  experienced ; 
that  is,  if  we  fleep  in  the  day-light,  anil  endeavour  to  fee  iome 

object 


Sect.  XVIII.  s-  OF  SLEEP. 


147 


pbjedt  in  our  dream,  the  light  is  exceedingly  painful  to  our 
1 eyes;  .and,  after  repeated  ftruggles,  we  lament  in  our  fleep, 
that  we  cannot  fee  it.  In  this  cafe  I app"ehend  the  eyelid  is 
in  fome  degree  opened  by  the  vehemence  of  our  fenfations; 
and  the  iris  being  dilated,  the  optic  nerve  fhews  as  great,  or 
greater  fenhbilicy  than  in  our  waking  hours.  See  No.  15.  of 
this  Sedfion. 

When  we  are  forcibly  waked  at  midnight  from  profound 
fleep,  our  eyes  ate  much  dazzled  with  the  light  of  the  candle  for 
a minute  or  two,  after  there  has  been  fufficient  time  allowed  for 
the  contraction  of  the  iris ; which  is  owing  to  the  accumulation 
of  fenforial  power  in  the  organ  of  vifion  during  its  ftate  of  lefs 
adtivity.  But  when  we  have  dreamt  much  ot  vitible  objedts, 
■this  accumulation  of  fenforial  power  in  the  organ  of  vifion  is 
leflened  or  prevented,  and  we  awake  in  the  morning  without 
being  dazzled  with  the  light,  after  the  iris  has  had  time  to  con- 
tradt  itfelf.  This  is  a matter  of  great  curiofity,  and  may  be  thus 
tried  by  any  one  in  the  dav-light.  Clofe  your  eyes,  and  cover 
them  with  your  hat;  think  for  a minute  on  a tune  which  you 
are  accuflomed  to,  and  endeavour  to  ling  it  with  as  little  adlivity 
of  mind  as  poflible.  Suddenly  uncover  and  open  your  eyes,  and 
in  one  fecond  of  time  the  iris  will  contra  dt  itfelf,  hut  you  will 
perceive  the  day  more  luminous  for  feveral  fcconds,  owing  to 
the  accumulation  of  fenforial  power  in  the  optic  nerve. 

Then  again  clofe  and  cover  your  eyes,  and  think  intenfely 
on  a cube  of  ivory  two  inches  diameter,  attending  firft  to  the 
north  and  fouth  tides  of  it,  and  then  to  the  other  four  tides  of  it ^ 
then  get  a clear  image  in  your  mind’s  eye  of  all  the  tides  of  the 
fame  cube,  coloured  red,  and  then  of  it  coloured  green,  and  then 
of  it  coloured  blue  ; laftly,  open  your  eyes  as  in  the  former  ex- 
periment, and  after  the  fir  ft  fecond  of  time  allowed  for  the  con- 
traction of  the  iris,  you  will  not  perceive  any  increafe  of  the 
light  of  the  day,  or  dazzling ; becaufe  now  there  is  no  accumu- 
lation of  fenforial  power  in  the  optic  nerve,  that  having  been 
expended  by  its  adtion  in  thinking  over  viftble  objedts. 

This  experiment  is  not  eafy  to  be  made  at  firft,  but  by  a few 
patient  trials  the  fadt  appears  very  certain,  and  fhews  clearly;, 
that  our  ideas  of  imagination  are  repetitions  ol  the  motions  of 
the  nerve,  which  were  originally  occalioned  by  the  ftimulus  of 
external  bodies ; becaufe  they  equally  expend  the  fenforial 
power  in  the  organ  ot  fenfe.  See  Sedt.  II  I.  4.  which  is  analogous 
to  our  being  as  much  fatigued  by  thinking  as  by  labour. 

6.  Nor  is  it  in  our  dreams  alone,  but  even  in  our  waking 
reveries,  and  in  great  efforts  of  invention;  lo  great  is  die  vi- 
vacity of  our  ideas,  that  we  do  not,  for  a time,  diftinguifti 

X them 


OF  SLEEP. 


r 48- 


Sect.  XVIII.  7,  S: 


them  from  the  real  prefence  of  fubflantial  objects;  though  the 
external  organs  of  fenfe  are  open,  and  lurroundtd  with  their 
ufual  ftimuli.  Thus,  w-hilft  I am  thinking  over  the  beautiful  J 
valley,'  through  which  I yefterday  travelled,  I do  not  perceive  I 
the  furniture  ot  my  room:  and  there  are  fome,  whofe  waking  • 
imaginations  are  fc  apt  to  run  into  perfect  reverie,  that  in  their  « 
common  attention  to  a favourite  idea,  they  do  not  hear  the  f 
voice  of  the  companion,  who  accofts  them,  unlcfs  it  is  re-  , 
peated  with  unufual  energy. 

This  perpetual  miflake  in  dreams  and  reveries,  where  our  a 
ideas  of  imagination  are  attended  with  a belief  of  the  prefence  I 
Of  external  objects,  evinces,  beyond  a doubt,  that  all  our  ideas  1 
are  repetitions  of  the  motions  of  the  nerves  of  fenfe,  bv  which  h 
they* were  acquired ; and  that  this  belief  is  not,  as  fome  late  * 
phiiofophers  contend,  an  inftinct  neceflarily  connedtcd  only  f 
with  cur  perceptions. 

7.  A curious  queltion  demands  our  attention  in  this  place  , 1 
as  we  uo  not  diflinguifh  in  our  dreams  and  reveries  between  s 
cur  perceptions  of  external  objedts,  and  our  ideas  of  them  in  ? 
their  abfence,  how  do  we  diftinguiih  them  at  any  time?  In  a • 
dream,  if  the  fweetnefs  of  fugar  occurs  to  my  imagination,  thc-J 
whitenefsandhardnefsot  it,  which  were  ideas  uiuallyconnc-dfed  j 
with  the  fweetnefs,  immediately  follow  in  the  train ; and  I be-  * 
lieve  a material  lump  of  fugar  pi  efent  before  my  fenfe*  : but  in  1 
my  waking  hours,  if  the  fweetnefs  occurs  to  my  imagination,  1 
the  ftimulus  of  the  table  to  my  hand,  or  ot  the  window  to  rr.v  f 
•eye,  prevents  the  other  ideas  of  the  hardnefs  and  whiteneis  cfj 
the  fugar  from  fucceedmg ; and  hence  I perceive  the  fallacy,  and 
ditbelieve  the  exigence  of  objects  correfpondent  to  thofe  ideas 
whofe  tribes  or  trains  are  broken  by  the  ftimulus  of  other  ob- 
jects. And  further,  in  our  waking  hours  we  frequently  exert 
our  volition  in  comparing  prefent  appearances  with  fuch  as  we 
have  uiuully  obferved ; and  thus  correct  the  errors  of  one  fenfe 
by  our  general  knowledge  ot  nature  by  intuitive  analogy.  See 
Sect.  XVII.  3.  7.  Whereas  in  dreams  the  pow  er  of  volition 

is  lufpended,  we  can  recollect  and  compare  our  preitnt  ideas 
with  none  of  our  acquired  knowledge,  and  are  hence  incapable 
ot  oblerving  any  abiurditics  in  them. 

By  this  ciiterion  we  diltinguifh.  our  waking  from  our  fleep- 
ing  hours ; we  can  voluntarily  recollect  our  fieeping  ideas,  w hen 
we  are  awuke,  and  compare  them  with  our  waking  ones;  but 
we  cannot  in  cur  lleep  voluntarily  recoiled!  our  waking  ideas 
at  ail. 

8.  The  vaft  variety  of  feenery,  novelty  of  combination, 
and  dnlinctnefs  of  .imagery,  are  oilier  curious  ciicumftances 

. of 


OF  SLEEP. 


Sj&eT.'XVni.  9, 10,  ii. 


49 


ef  our  Peeping  imaginations.  The  variety  of  fcenery -Teems 
to  arife  from  the  fuperior  activity  and  excellence  of  our  fenfe 
of  vifion  ; which,  in  an  inftant,  unfolds  to  the  mind  extenhve 
fields  of  pleafureable  ideas,  while  the  other  fenfes  colleft  their 
objecfs  flowly,  and  with  little  combination.;  add  to  this,  that 
the  ideas,  which  this  organ  prefents  us  with,  are  more  fre- 
quently conceited  with  our  fenfation  than  thofe  of  any  other. 

9.  The  great  .novelty  of  combination  is  owing  to  another 
circumftance ; the  trains  of  ideas,  which  are  carried  on  in  our 
waking  thoughts,  are,  in  our  dreams,  duTevered  in  a thoufand 
places,  by  the  iufpenlion  of  volition,  and  the  abfence  of  irri- 
gative ideas,  and  are  hence  perpetually  falling  into  new  cate- 
nations, as  explained  in  Se£t.  XVI.  1.  9.  For  the  power  of 
•volition  is  perpetually  exerted  during  our  waking  hours,  in 
.comparing  our  palling  trains  of  ideas  with  our  acquired  know- 
ledge of  nature,  and  thus  forms  many  intermediate  links  in  their 
-catenation.  And  the  irritative  ideas  excited  by  the  ftimulus  of 
the  objects,  with  which  we  are  furrounded,  are  every  moment 
intruded  upon  us,  and  form  other  links  of  our  uncealmg  ca- 
tenations ot  ideas. 

10.  The  abfence  of  the  ftimuli  of  external  bodies,  and  of 
volition,  in  our  dreams,  renders  the  organs  of  fenfe  liable  to  be 
more  ftrongly  affefted  by  the  powers  of  fenfation,  and  of  af- 
fociation.  For  our.delires  or  averfions,  or  the  obtruiions  of 
furrounding  bodies,  .diflever  the  fenlitive  and  affociate  tribes  of 
ideas  in  our  waking  hours,  by  introducing  thofe  -pf  irritation 
and  volition  amongft  them.  Hence  proceeds  the  fuperior  dif- 
tinftnefs  of  pleafureable  or  painful  imagery  in  our  fleep : for 
we  recal  the  figure  and  the  features  of  a long  loft  friend,  whom 
we  loved,  in  our  dreams,  with  much  more  accuracy  and  vi- 
vacity than  in  our  waking  thoughts.  This  circumftance  con- 
tributes to  prove,  that  our  ideas  of  imagination  are  reiterations 
of  thofe  motions  of  our  organs  Gf  fenfe,  which  were  excited 
by  external  objeffs ; becaule,  while  we  are  expofed  to  the  fti- 
muli of  prefent  objects,  our  ideas  of  abfent  objects  cannot  be 
fo  diftindfly  formed. 

11.  The  rapidity  of  the  fucceffion  of  tranfactions  in  our 
-dreams  is  almoft  inconceivable  ; infomuch,  that  when  we  are 
accidentally  awakened  by  the  jarring  of  a door  which  is  open- 
ed into  our  bed-chamber,  we  fometimes  dream  a whole  hiftory 
of  thieves  or  lire  in  the  very  inftant  of  awaking. 

During  the  fulpenfton  of  volition  we  cannot  compare  our 
other  ideas  with  thofe  of  the  parts  of  time  in  which  they  exift; 
that  is,  we  cannot  compare  the  imaginary  fcene,  which  is  be- 
fore us,  with  thofe  changes  of  it  which  precede  or  follow  it, 

becaufe 


OF  SLEEP. 


Sect.  XVIII.  12. 


153 

becaufe  this  act  of  comparing  requires  recollection  or  voluntarv 
exertion : whereas,  in  our  waking  hours,  we  are  perpetually 
making  this  comparifon,  and  by  that  means  our  waking  ideas 
are  kept  confident  with  each  other  by  intuitive  analogy;  but 
this  comparifon  retards  the  fuccelTion  of  them,  bv  occasioning 
their  repetition.  Add  to  this,  that  the  tranfadlions  of  our  dreams 
conlift  chiefly  of  vifible  ideas,  and  that  a whole  hiftory  of 
thieves  and  fire  may  be  beheld,  in  an  inftant  of  time,  tike  the 
figures  in  a pidture. 

12.  From  this  incapacity  of  attending  to  the  parts  of  time  in 
our  dreams,  arifes  our  ignorance  of  the  length  of  the  night; 
which,  but  from  our  conftant  experience  to  the  contrary,  we 
fhould  conclude  was  but  a few  minutes  when  our  fleep  is  per- 
fect. The  fame  happens  in  our  reveries:  thus,  when  we  are 
pofleffed  with  vehement  ioy',  grief,  or  anger,  time  appears  ihort, 
for  we  exert  no  volition  to  compare  the  prefent  fcenery  with 
the  pad  or  future ; but  when  we  are  compelled  to  perform  thole 
exercifes  of  mind  or  body,  which  are  unmixed  with  pafiion,  as 
in  travelling  over  a dreary  country,  time  appears  long ; for  our 
delire  to  finifh  our  journey  occafions  us  more  frequently  to 
compare  our  prefent  fituation  with  the  parts  of  time  or  place 
which  are  before  and  behind  us. 

So,  when  we  are  enveloped  in  deep  contemplation  of  any 
kind,  or  in  reverie,  as  in  reading  a very  interefting  play  or  ro- 
mance, we  meafure  time  very  inaccurately ; and  hence,  if  a 
play  greatly  affects  our  palfions,  the  abfurdity  of  palfing  over 
many  days  or  years,  and  of  perpetual  changes  of  place,  are  not 
perceived  by  the  audience,  as  is  experienced  by  every  one  who 
reads  or  fees  fome  plays  of  the  immortal  Shakefpeare;  but  it 
is  necefiary  for  inferior  authors  to  obferve  thofe  rules  of  the 
iriQttvov  and  irgeTrov  inculcated  by  Arillotle,  becaufe  their  works  do 
not  intereft  the  palfions  fufficiently  to  produce  complete  reverie. 

Thole  works,  however,  whether  a romance,  or  a fermon, 
which  do  not  inferelfl  us  fo  much  as  to  induce  reverie,  may, 
neverthelefs,  incline  us  to  fleep.  For  thole  pleafureable  ideas, 
which  are  prefented  to  us,  and  are  too  gentle  to  excite  laugh- 
ter, (which  is  attended  with  interrupted  voluntary  exertions, 
as  explained  Seel.  XXXIV.  1.  4.)  and  which  are  not  accom- 
panied with  any  other  emotion,  which  ufually  excites  tome  vo- 
voluntary  exertion,  as  anger,  or  fear,  are  liable  to  produce 
fleep ; which  coniifts  in  a fufpenfion  of  all  voluntary  power. 
But  if  the  ideas  thus  prefented  to  us,  and  interelf  our  atten- 
tion, are  accompanied  with  io  much  pleafureable  or  painful 
jenfation  as  to  excite  our  voluntary  exertion  at  the  lame  time, 
reverie  is  the  confequence.  Hence,  an  interefting  play  pre- 
duces 


OF  SLEEP. 


Sect.  XVIII.  13, 14. 


J5* 


duces  reverie,  a tedious  one  produces  fleep : in  the  latter  we 
become  exhaufted  by  attention,  and  are  not  excited  to  any 
voluntary  exertion,  and  therefore  fleep ; in  the  former  we  are 
excited  by  fome  emotion,  which  prevents,  by  its  pain,  the  fuf- 
penflon  of  volition,  and  in  as  much  as  it  interefts  us,  induces 
reverie,  as  explained  in  the  next  Sedfion. 

But  when  our  fleep  is  imperfedt,  as  when  we  have  deter- 
mined to  rife  in  half  an  hour,  time  appears  longer  to  us  than  in 
mod  other  fltuations.  Here  our  folicitude  not  to  overfleep  the 
determined  time,  induces  us,  in  this  imperfect  fleep,  to  compare 
the  quick  changes  of  imagined  fcenery  with  the  parts  of  time  or 
place  they  would  have  taken  up,  had  they  real  exiftence ; and 
that  more  frequently  than  in  cur  waking  hours ; and  hence  the 
time  appears  longer  to  us : and  I make  no  doubt  but  the  per- 
mitted time  appears  long  to  a man  going  to  the  gallows,  as  the 
fear  of  its  quick  lapfe  will  make  him  think  frequently  about  it. 

13.  As  we  gain  our  knowledge  of  time  by  comparing  the 
prefent  fcenery  with  the  part  and  future,  . and  of  place  by  com- 
paring the  fltuations  of  objects  with  each  other:  fo  we  gain  our 
idea  of  confcioufnefs  by  comparing  ourfelves  with  the  fcenery 
around  us ; and  of  identity  by  comparing  our  prefent  confciouf- 
nefs with  our  part:  confcioufnefs : as  we  never  think  of  time  or 
place,  but  when  we  make  the  companions  above  mentioned ; fo 
we  never  think  of  confcioufnefs,  but  when  we  compare  our  own 
exiftence  with  that  of  other  objedts;  nor  of  identity,  but  when 
we  compare  our  prefent  and  our  paft  confcioufnefs.  Hence  the 
confcioufnefs  of  our  own  exiftence,  and  of  our  identity,  is  owing 
to  a voluntary  exertion  of  our  minds : and  on  that  account,  in 
our  complete  dreams  we  neither  meafure  time,  are  furprifed  at 
the  fudden  changes  of  place,  nor  attend  to  our  own  exiftence  or 
identity,  becaufe  our  power  of  volition  is  fufpended.  But  all 
thele  circumftances  are  more  or  lefs  obfervable  in  our  incom- 
plete ones ; for  then  we  attend  a little  to  the  lapfe  of  time  and 
the  changes  of  place,  and  to  our  own  exiftence,  and  even  to  our 
identity  of  perfon  ; for  a lady  feldom  dreams  that  fhe  is  a foldier ; 
nor  a man,  that  he  is  brought  to  bed. 

14.  As  long  as  our  fenfations  only  excite  their  fenfual  mo- 
tions, or  ideas,  our  fleep  continues  found ; but  as  foon  as  they 
exite  defires  or  averflons,  our  fleep  becomes  imperfedt ; and 
when  that  defire  or  averlion  is  fo  ftrong  as  to  produce  volun- 
tary motions,  we  begin  to  awake ; the  larger  mufcles  of  the 
body  are  brought  into  adtion,  to  remove  that  irritation  or  fen- 
fation,  which  a continued  pofture  has  caufed  ; we  ftretch  our 
limbs,  and  yawn,  and  our  fleep  is  thus  broken  by  the  accumu- 
lation of  voluntary  power. 

Sometimes 


OF  SLEEP. 


Sect.  XVIII.  u 


*S2 

Sometimes  it  happens,  that  the-adb  of  waking  is  fuddenlv 
produced,  and  this  i'oon  after  the  commencement  of  fleep  ; 
•which  is  occafioned  by  fome  fenfation  fo  difagreeable,  as  in- 
jflantaneouflv  to  excite  the  power  of  volition  ; and  ■ a temporary 
action  of  all  the  voluntary  motions  fuddenlv  fucceeds,  and  we 
Hart  awake.  This  is  fometimes  accompanied  with  loud  noife 
in  the  ears,  and  with  lome  degree  of  fear;  and  wlien  it  is  in 
great  excefs,  fo  as  to  produce  continued  convuHtve  motion'  of 
thole  mufcles,  which  are  generally  fubfervient  to  volition,  11 
becomes  epilepfy  ; tlie  fits  of  which,  in  fome  patients,  generally 
commence  during  flee]).  This  differs  from  the  nightmare,  de- 
feribed  in  No.  3.  of  this  Section,  becaufe  in  that  the  -c'ingree- 
able  fenlation  is  not  fo  great  as  to  excite  the  power  of  volition 
into  arition  ; for  as  loon  as  that  happens,  the  difeafe  ccafes. 

Another  circumftance,  which  fometimes  awakes  people  foon 
after  the  commencement  of  their  fleep,  is  where  the  voluntary 
power  is  already  io  great  in  quantity,  as  almoft  to  prevent  them 
from  falling  afleep,  and  then  a little  accumulation  of  it  foon 
again  awakens  them;  this  happens  in  cafes  of  infinity,  or 
where  the  mind  has  been  lately  much  agitated  bv  fear  or  anger. 
There  is  another  circumftance  in  which  fleep  is  likcwile  of 
fhort  duration,  which-arjfes  trom  great  debility,  as  after  great 
over-fatigue,  and  in  fome  fevers,  where  the  ftrength  of  the  pa-  ‘ 
tient  is  greatly  dimini fired ; as  in  thefe  cafes  the  pulfe  inter- 
mits or  flutters,  and  the  refpiration  is  previouflv  affected,  it 
feerns  to  originate  from  the  want  of  fome  voluntary  efforts  to, 
facilitate  refpiration,  as  when  we  are  awake ; and  is  further 
treated  of  in  -vol.  ii.  Clafs  i.  2.  1,  2.  on  the  Difeafes  of  the 
Voluntary  Lower.  Art.  Somnus  interruptus. 

15.  We  come  now  to  thofe  motions  which  depend  on  irrita- 
tion. ‘ The  motions  of  the  arterial  and  glandular  Ivftems  continue  ■ 
in  our  fleep,  proceeding  flower  indeed,  but  ftronger  and  morel 
uniformly,  than  in  our  waking  hours,  when  thev  tfre  incom- 
moded by  external  ftimuli,  or  by  the  movements  of  volition:  the 
motions  of  the  mulcles  fubfervient  to  refpiration  continue  to  he 
ftimulated  into  action  ; and  the  other  internal  fe-nfes  of  hunger, 
thirft,  and  luff,  are' not  only  occuiionaliv  excited  in  our  fleep,  hut 
their  irritative  motions  are  fucceeded  bv  their  uiual  lenfations, 
and  make  a part  of  the  farrago  ot  our  dreams.  Thefe  fenfations 
of  the  want  of  air,  of  hunger,  thirft,  and  luft,  in  our  dreams, 
contribute  to  prove,  that  the  nerves  ot  the  external  fenfes  are 
alfo  alive  and  excitable  in  cur  fleep  ; but  as  the  ftimuli  of  exter- 
nal objedts  are  either  excluded  trom  them  by  the  darknels  and 
iilence  of  the  night,  or  their  accels  to  them  is  prevented  bv  die 
fufpenlion  of  volition,  thefe  nerves  of  lenfe  fall  more  readilv  into 


OF  SLEEP. 


*53 


Sect.  XVIII.  15. 

their  connections  with  fenfation  and  with  afiociation;  becaufe 
much  fenforial  power,  which,  during  the  day,  was  expended  in 
moving  the  external  organs  of  fenfe  in  confequence  of  irritation 
from  external  ftimuli,  or  in  confequence  ot  volition,  becomes 
now  in  fome  degree  accumulated,  and  renders-  the  internal  or 
immediate  organs  of  fenfe  more  eallly  excitable  by  the  other 
fenforial  powers.  Thus,  in  refpeCt  to  the  eye,  the  irritation 
from  external  ftimuli,  and  the  power  of  volition  during  our  wak- 
ing hours,  elevate  the  eyelids,  adapt  the  aperture  ot  tire  iris  to 
the  quantity  of  light,  the  focus  of  the  cryftalline  humour,  and 
the  angle  of  the  optic  axiles  to  the  diftance  of  the  obiedf ; all 
which  perpetual  adlivitv  during  the  day  expends  much  ienforial 
power,  which  is  laved  during  our  lleep. 

Hence  it  appears,  that  not  only  thofe  parts  of  the  fyftera 
which  are  always  excited  by  internal  ftimuli,  as  the  ftomacru, 
inteftinal  canal,  bile-duCts,  and  the  various  glands ; but  the  or- 
gans of  fenfe  alfo,  may  be  more  violently  excited  into  action  by 
the  irritation  from  internal  ftimuli,  or  by  fenfation,  during  our 
lleep,  than  in  our  waking  hours ; becauie,  during  the  fufpen- 
fton  of  volition,  there  is  a greater  quantity  ot  the  fpirit  of  ani- 
mation to  be  expended  by  the  other  fenforial  powers.  On  this 
account  our  irritability  to  internal  ftimuli,  and  our  fenfibility 
to  pain  or  pleafure,  is  not  only  greater  in  lleep,  but  increafes 
as  our  lleep  is  prolonged.  Whence  digeftion  and  fecretion  are 
performed  better  in  lleep  than  in  our  waking  hours;  and  our 
dreams  in  the  morning  have  greater  variety  and  vivacity,  as  our 
lenfibility  increafes,  than  at  night  when  we  ftrft  lie  down.  And 
hence,  epileptic  fits,  which  are  always  occafioned  by  fome  dif- 
agreeable  fenfation,  fo  frequently  attack  thofe  who  are  fubjedt 
to  them,  in  their  lleep  ; becauie,  at  this  time,  the  fyftem  is  more 
excitable  by  painlul  fenfation,  in  confequence  of  internal  fti- 
muli ; and  the  power  of  volition  is  then  luddenly  exerted  to  re- 
lieve this  pain,  as  explained  Sedi.  XXXIV.  1.  4, 

There  is  a difeafe  which  frequently  affedls  children  in  the 
cradle,  which  is  termed  ecftacy,  and  feems  ro  conftft  in  certain 
exertions  to  relieve  painful  fenfation,  in  which  the  voluntary 
power  is  not  fo  far  excited  as  totally  to  awaken  them,  and  yet 
is  fumcieat  to  remove  the  diliigreeable  fenfation  which  excites 
it ; in  this  cafe  changing  the  pofture  of  the  child  frequently  re- 
lieves it. 

I have  at  this  time  under  my  care  an  elegant  young  man, 
about  twenty-two  years  ol  age,  who  feldom  fleeps  more  tha*t 
an  hour  without  experiencing  a convullion  fit,  which  ceafes  in 
about  half  a minute  without  any  fubfequent  ftupor.  Large 
Holes  of  opium  only  prevented  the  paroxyfms,  fo  long  as  they 


OF  SLEEP. 


*54 


Sect.  XVIII.  15. 


prevented  him  from  Peeping  by  the  intoxication  which  they  in- 
duced. Other  medicines  had  no  effeCt  on  him.  He  was  gently- 
awaked  every  half  hour  for  one  night,  hut  without  good  effeci, 
as  he  foon  flept  again,  and  the  fit  returned  at*  about  the  fame  pe- 
riods of  time ; for  the  accumulated  ffenforial  power,  which  oc- 
casioned the  increafed  fenfibility  to  pain,  was  not  thus  exhauPed. 
This  cafe  evinces,  that  the  fenfibility  of  the  fyPem  to  internal 
excitation  increafes  as  our  Sleep  is  prolonged,  till  the  pain  thus 
hccaiioned  produces  voluntary  exertion;  which,  when  it  is  in 
its  ufual  degree,  only  awakens  us ; but  when  it  is  more  violent, 
it  occafions  convulfions. 

The  cramp  in  the  calf  of  the  leg  is  another  kind  of  convulfion 
which  generally  commences  in  Peep,  occafioned  by  the  conti- 
nual increafe  of  irritability  from  internal  Pimuli,  or  of  fenfibili- 
ty, during  that  Pate  of  our  exiPence.  The  cramp  is  a violent 
exertion  to  relieve  pain,  generally  either  of  the  fkin  from  cold, 
or  of  the  bowels,  as  in  feme  diarrhoeas,  or  from  the  mufcles 
having  been  previouPy  overpretched,  as  in  walking  up  or  down 
Peep  hills.  But  in  thefe  convulfions  of  the  mufcles  which  form 
the  calf  of  the  leg,  the  contraction  is  fo  violent  as  to  occalion 
another  pain  in  confequence  of  their  own  too  violent  contrac- 
tion, as  foon  as  the  original  pain  which  caufed  the  contraction 
is  removed.  And  hence  the  cramp,  or  fpal’m,  of  thefe  mufcles 
is  continued  without  intermiPion  by  this  new  pain,  unlike  the 
alternate  convulfions  and  remifiions  in  epileptic  fits.  The  reafon 
that  the  contraction  of  thefe  mufcles  of  the  calf  ct  the  leg  ij 
more  violent  during  their  convulfion  than  that  of  others,  de- 
pends on  the  weaknefs  of  their  antagoniP  mufcles ; for  after 
thele  have  been  contracted  in  their  ufual  aCtion,  as  at  every 
Pep  in  walking,  they  are  again  extended,  not,  as  mop  other 
mufcles  are,  by  their  antagoniPs,  but  by  the  weight  of  the 
whole  body  on  the  balls  of  the  toes ; and  that  weight  applied 
to  great  mechanical  advantage  on  the  heel,  that  is,  on  the  otiier 
end  of  the  bone  of  the  foot,  which  thus  aCts  as  a lever. 

Another  difeafe,  the  periods  of  which  generally  commence 
during  our  Peep,  is  the  aPhma.  Whatever  mav  be  the  re- 
mote caufe  of  paroxyfms  of  aPhma,  the  immediate  cauie  of 
the  cenvullive  relpiration,  whether  in  the  common  aPhma,  or 
in  what  is  termed  the  convulfive  aPhma,  which  are  perhaps 
only  diPerent  degrees  ot  the  fame  difeafe,  mup  be  owing  to 
violent  voluntary  exertions  to  relieve  pain,  as  in  other  con- 
vulfions ; and  the  increafe  of  irritability  to  internal  Pimuli,  or 
of  fenfibility  during  Peep,  mup  occafion  them  to  commence 
at  this  time. 

Debilitated  people,  who  have  been  unfortunately  accuftomcJ 


•»*«.-  ■ o mra.  ..  : -j 


Sect.  XVIII.  16. 


OF  SLEEP. 


I5S 

to  great  ingurgitation  of  fpirituous  potation,  frequently  part 
with  a great  quantity  of  water  during  the  night,  but  with  not 
more  than  ufual  in  the  day-time.  This  is  owing  to  a be- 
ginning torpor  of  the  abforbent  fyftem,  and  precedes  anafarca, 
which  commences  in  the  day,  but  is  cured  in  the  night  by  the 
increafe  of  the  irritability  of  the  abforbent  fyftem  during  lleep, 
which  thus  imbibes,  from  the  cellular  membrane,  the  fluids  which 
had  been  accumulated  there  during  the  day ; though  it  is  pof- 
fible  the  horizontal  polition  of  the  body’  may  contribute  fome- 
thing  to  this  purpofe,  and  alfo  the  greater  irritability  of  fome 
branches  of  the  abforbent  veffels,  which  open  their  mouths  in 
die  cells  of  the  cellular  membrane,  than  that  of  other  branches. 

As  foon  as  a perfon  begins  to  deep,  the  irritability  and  fen- 
fibility  of  the  fyftem  begin  to  increafe,  owing  to  the  fufpenfion 
of  volition  and  the  exclufion  of  external  ftimuli.  Hence  the 
aftions  of  the  veffels,  in  obedience  to  internal  ftimulation,  be- 
come ftronger  and  more  energetic,  though  lefs  frequent  in  re- 
fpedt  to  number.  And  as  many  of  the  fecretions  are  increafed, 
fo  the  heat  of  the  fyftem  is  gradually  increafed ; and  the  extremi- 
ties ot  feeble  people,  which  had  been  cold  during  the  day,  be- 
come warm.  Towards  morning  many  people  become  fo 
warm,  as  to  find  it  neceffary  to  throw’  off  fome  of  their  bed- 
clothes, as  foon  as  they  awake;  and  in  others  fweats  are  fo 
liable  to  occur  towards  morning  during  their  fleep. 

Thus,  thofe  who  are  not  accuftomed  to  fleep  in  the  open 
air,  are  very  liable  to  takd  cold,  if  they  happen  to  fall  afleep 
on  a garden  bench,  or  in  a carriage  with  the  window  open : 
for,  as  the  fyftem  is  warmer  during  fleep,  as  above  explained, 
if  a current  of  cold  air  affedts  any  part  of  the  body,  a torpor 
of  that  part  is  more  effectually  produced,  as  when  a cold  blaft: 
of  air  through  a key-hole  or  cafement  falls  upon  a perfon  in  a 
warm  room.  In  thofe  cafes  the  affected  part  poffeffes  lefs  irri- 
tability in  refpedt  to  heat,  from  its  having  previoufly  been  ex- 
pofed  to  a greater  ftimulus  of  heat,  as  in  the  warm  room,  or 
during  fleep ; and  hence,  when,  the  ftimulus  of  heat  is  diminifh- 
ed,  a torpor  is  liable  to  enfue ; that  is,  we  take  cold.  Hence, 
people  who  fleep  in  the  open  air  generally  feel  chilly  both  at 
the  approach  of  fleep  and  on  their  awaking ; and  hence  many 
people  are  perpetually  fubjedt  to  catarrhs  if  they  fleep  in  a lefs 
warm  head-drels  than  that  which  they  wear  in  the  day. 

1 6.  Not  only  the  fenforial  powers  of  irritation  and  of  fen- 
fation,  but  that  of  affcciation  alfo  appear  to  adt  with  greater 
vigour  during  the  fufpenfion  of  volition  in  fleep.  It  will  be 
fhewn  in  another  place,  that  the  gout  generally  firft  attacks  the 
liver,  and  that  afterwards  an  inflammation  of  the  ball  of  the 

Y great 


OF  SLEEP. 


Sect.  XVIII.  16. . 


156 

great  toe  commences  by  affociation,  and  that  of  the  liver  ceafes. 
Now,  as  this  change  or  metaftalis  of  the  activity  of  the  fyftem  , 
generally  commences  in  deep,  it  follows,  that  thefe  affociations 
of  motion  exift  with  greater  energy  at  that  time;  that  is,  that 
the  fenforial  faculty  of  affociation,  like  thofe  of  irritation  and 
of  fenfation,  becomes  in  fome  meafure  accumulated  during  the 
fufpenfion  of  volition. 

Other  affociate  tribes  and  trains  of  motions,  as  well  as  the 
irritative  and  fenfitive  ones,  appear  to  be  increafed  in  their  ac- 
tivity during  the  fufpenfion  of  volition  in  deep:  2s  thofe  which  . 
contribute  to  circulate  the  blood,  and  to  perform  the  various  1 
fecretions,  as  well  as  the  aflociate  tribes  and  trains  of  ideas,  1 
■which  contribute  to  furnifh  the  perpetual  dreams  of  our  dream- 
ing imaginations. 

In  deep,  the  fecretions  have  generallv  been  fuppofed  to  be 
diminifhed,  as  the  expectorated  mucus  in  coughs,  the  fluids 
difeharged  in  diarrhoeas,  and  in  falivation,  exdept  indeed  the 
fecretion  of  fweat,  which  is  often  vtflbly  increafed.  This  er-  ; 
ror  feems  to  have  arifen  from  attention  to  the  excretions,  rather 
than  to  the  fecretions.  For  tire  fecretions,  except  that  of  fweat, 
are  generally  received  into  refervoirs,  as  the  urine  into  the  blad- 
der, and  tire  mucus  of  the  inteflines  and  lungs  into  their  re- ) 
fpe&ive  cavities;  but  thefe  refervoirs  do  not  exclude  thefe  fluids  j| 
immediately  by  their  ftimulus,  hut  require,  at  the  fame  time, ' 
fomc  voluntary  efforts,  and  therefore  permit  them  to  remain 
during  deep.  And  as  they  thus  continue  longer  in  thofe  re- 
ceptacles in  our  deeping  hours,  a greater  part  is  ahforhed  from 
them,  and  rite  remainder  becomes  thicker,  and  fometimes  in 
lefs  quantity,  though  at  the  time  it  was  ferreted,  the  fluid  was 
in  greater  quantity  than  in  our  waking  hours.  Thus,  the 
urine  is  higher  coloured  after  long  deep;  which  fhews  that  a 
greater  quantity  has  been  fecreted,  and  that  more  of  the  aque- 
ous and  inline  part  has  been  re-abforbed,  and  the  earthv  part 
left-  in  the  bladder : hence,  thick  urine  in  fevers  fhews  only  a 
greater  action  of  the  veffels  which  fecrete  it  in  the  kidneys, 
and  of  thofe  which  abforb  it  from  the  bladder. 

The  fame  happens  to  the  mucus  expectorated  in  coughs, 
which  is  thus  thickened  by  abforption  of  its  aqueous  and  faiinc 
parts,  and  the  fame  ot  the  feces  of  the  inteflines.  From  hence 
it  appears,  and  trom  what  has  been  laid  in  No.  15,  of  this  Sec- 
tion, concerning  the  increafe  of  irritability  and  of  fendbility 
tluring  deep,  that  the  fecretions  are,  in  general,  rather  increat- 
ed  than  diminithed  during  thefe  hours  of  our  cxiltence  ; and  it  is 
probable  that  nutrition  is  almoft  entirely  performed  in  deep ; 
and  that  young  animals  grow  more  at  this  time  than  in  their 

waking 


157 


Sect.  XVIII.  17,18.  OF  SLEEP. 

waking  hours,  as  young  plants  have  long  fince  been  obferved 
to  grow  more  in  the  night,  which  is  their  time  of  fleep. 

17.  Two  other  remarkable  circumftances  of  our  dreaming 
ideas  are  their  inconfiftency,  and  the  total  abfence  of  furprife. 
Thus  we  feem  to  be  prefent  at  more  extraordinary  metamor- 
phofes  of  animals  or  trees,  than  are  to  be  met  with  in  the  fa  - 
bles of  antiquity  ; and  appear  to  be  tranfported  from  place  to 
place,  which  feas  divide,  as  quickly  as  the  changes  of  fcenery 
are  performed  in  a play-houfe ; and*  yet  are  not  fenfible  of  their 
inconfiftency,  nor  in  the  leaft  degree  affedfed  with  furprife. 

We  muft  .conftder  this  circumftance  more  minutely.  In  our 
waking  trains  . of  ideas,  thofe  that  are  inconiiftent  with  the  ufual 
order  of  nature  fo  rarely  have  occurred  to  us,  that  their  con- 
nedfion  is  the  flighted  of  all  others  : hence,  when  a confident 
train  of  ideas  is  exhaufted,  we  attend  to  the  external  ftimuli 
drat  ufually  furround  us,  rather  .than  to  any  inconiiftent  idea 
which  might  otherwife  prefent  itfelf : and  if  an  inconfiftent  idea 
fhould  intrude  itfelf,  we  immediately  compare  it  with  the  pre- 
ceding one,  and  voluntarily  rejedt  the  train  it  would  introduce. 
This  appears  further  in  the  Section  on  Reverie,  in  which  ftate 
of  the  mind  external  ftimuli  are  not  attended  to,  and  yet  the 
flreams  of  ideas  are  kept  confident  by  the  efforts  of  .volition. 
But  as  our  faculty  of  volition  is  fufpended,  and  all  external 
ftimuli  ace  .excluded  in  fleep,  this  {lighter  connedtion  of  ideas 
takes  place,  and  the  train  is  faid  to  he  inconfiftent;  that  is, 
diffimilar  to  the  ufual  order  of  nature. 

But,  when  any  confiftent  train  of  fenfitive  or  voluntary  ideas 
is  flowing  along,  if  any  external  ftimulus  affects  us  fo  violent- 
ly as  to  intrude  irritative  ideas  forcibly  into  the  mind,  it  dif- 
unites  the  former  train  of  ideas,  and  we  are  affedled  with  fur- 
prife. Thefe  ftimuli  of  unulual  energy  or  novelty,  not  only 
difunite  our  common  trains  of  ideas,  but  the  trains  of  mufcu- 
lar  motions  alfo,  which  have  not  been  long  eftablifhed  by  ha- 
bit, and  difturb  thofe  that  have.  Some  people  become  motion- 
lefs  by  great  furprife  : the  fits  of  hiccough  and  of  ague  have 
been  often  removed  by  it ; and  it  even  affedts  the  movements 
of  the  heart  and  arteries  : but  in  our  fleep,  all  external  ftimuli 
are  excluded,  and  in  confcquence  no  furprife  can  exift.  See 
Sedf.  XVII.  3.7. 

18.  We  frequently  awake  with  pleafure  from  a dream, 
which  has  delighted  us,  without  being  able  to  recoiled!  the 
tranfadfions  of  it ; unlefs  perhaps  at  a diftance  of  time,  feme 
analogous  idea  may  introduce  afrefh  this  forgotten  train ; and, 
in  our  waking  reveries,  we  fometimes  in  a moment  lofe  the 
Vain  of  thought,  but  continue  to  feel  the  glow  of  pleafure,  or 

' the 


158  OF  SLEEP.  Sect.  XVIII.  1 9, 20. 

the  depreflion  of  fpirits,  it  occafioned : whilft,  at  other  times,  we 
can  retrace  with  eafe  thefe  hiftories  of  our  reveries  and  dreams. 

The  above  explanation  of  furprife  throws  light  upon  this 
fubjedl.  When  we  are  fuddenly  awaked  by  any  violent  fti- 
mulus,  the  furprife  totally  difunites  the  trains  ot  our  fleeping 
ideas  from  thofe  of  our  waking  ones;  but  if  we  gradually 
awake,  this  does  not  happen;  and  we  readily  umavel  the  pre- 
ceding trains  of  imagination. 

19.  There  are' various  degrees  of  furprife;  the  more  intent 
we  are  upon  the  train  of  ideas  which  we  are  employed  about* 
the  more  violent  muff  be  the  ffimulus  that  interrupts  them,  and 
the  greater  is  the  degree  of  furprife.  I have  obferved  dogs, 
who  have  flept  by  the  fire,  and  by  their  obfcure  barking  and 
ftruggling  have  appeared  very  intent  on  their  prey,  that  (hew- 
ed great  furprife  for  a few  feconds  after  their  awaking, 
by  looking  eagerly  around  them;  which  they  'did  not  do  at 
other  times  of  waking.  And  an  intelligent  friend  of  mine 
has  remarked,  that  his  ladv,  who  frequently  fpeaks  much  and 
articulately  in  her  fleep,  could  never  recollect  her  dreams  in  the 
morning,  when  this  happened  to  her : but  that  when  fhe  did 
not  fpeak  in  her  fleep,  fhe  could  always  recolledt  them. 

Hence,  when  our  fenfations  adt  fo  ffrongly  in  fleep  as  to 
influence  the  larger  mufcles,  as  in  thofe  who  talk  or  ftruggle 
in  their  dreams,  or  in  thole  who  are  affedted  with  complete 
reverie,  (as  defcribed  in  the  next  Sedtion)  great  furprife  is 
produced  when  they  awake ; and  thefe,  as  well  as  thofe  who 
are  completely  drunk  or  delirious,  totally  forget  afterwards 
their  imaginations  at  thole  times. 

20.  As  the  immediate  cauie  of  fleep  confifls  in  the  fufpen- 
iion  of  volition,  it  follows,  that  whatever  diminifhes  the  gene- 
ral quantity  of  fenforial  power,  or  derives  it  from  the  faculty 
of  volition,  will  conftitute  a remote  caufe  of  fleep ; fuch  'as 
fatigue  from  mufcular  or  mental  exertion,  which  diminifhes  the 
general  quantity'  of  fenforial  power;  or  an  increafe  of  thelen- 
jitive  motions,  as  by  attending  to  foft  mufic,  which  diverts  the 
fenforial  power  from  the  faculty  of  volition ; or  laftly,  by  in- 
creafe of  the  irritative  motions,  as  by  wine,  or  food,  or  warmth; 
which  not  only,  by  their  expenditure  of  fenforial  power,  di- 
minifh  the  quantity  of  volition  ; but  alfo,  by  -their  producing 
pleafureable  fenfations  (which  occaflon  other  mufcular  or  feniuai 
motions  in  confequence)  doubly  decreafe  the  voluntary  power, 
and  thus  more  forcibly  produce  fleep.  See  Sedt.XXXlY.  1.  4. 

Another  method  of  inducing  fleep  is  delivered  in  a very  in- 
genious work  lately  pubhfhed  by  Dr.  Beddoes  ; who,  after  la- 
menting that  opium  frequently  occafions  re  file  Chiefs,  thinks, 

“ that 


OF  SLEEP, 


Sect.  XVIII.  20. 


*59 


« that  in  mod:  cafes  it  would  be  better  to  induce  deep  by  the 
abftra&ion  of  ftimuli,  than  by  exhaufting  the  excitability;” 
and  adds,  “ upon  this  principle,  we  could  not  have  a better 
foporiftc  than  an  atmofphere,  with  a diminifhed  proportion  of 
jDxygene  air,  and  that  common  air  might  be  admitted  after  the 
patient  was  afleep.”  (Obferv.  on  Calculus,  &c.  by  Dr.  Bed- 
does.  Murray.)  If  it  fhould  be  found  to  be  true,  that  the  ex- 
citability of  the  fyftem  depends  on  the  quantity  of  oxygene 
abforbed  by  the  lungs  in  refpiration,  according  to  the  theory  of 
Dr.  Beddoes,  and  of  M.  Girtanner,  this  idea  of  deeping  in  an 
atmofphere,  with  lefs  oxygene  in  its  compofition,  might  be  of 
great  lervice  in  epileptic  cafes,  and  in  cramp,  and  even  in  fits 
of  the  afthma,  where  their  periods  commence  from  the  increafe 
of  irritability  during  deep. 

Sleep  is  likewife  faid  to  be  induced  by  mechanic  preflure  on 
the  brain,  in  the  cafes  of  fpina  bifida.  Where  there  has  been 
a defefil  of  one  ©f  the  vertebrae  of  the  back,  a tumour  is  pro- 
truded in  confequence ; and,  whenever  this  tumour  has  been 
compreffed  by  the  hand,  deep  is  faid  to  be  induced,  becaufe  the 
whole  of  the  brain,  both  within  the  head  and  fpine,  becomes 
comprefied  by  the  retroceffion  of  the  fluid  within  the  tumour. 
But  by  what  means  a comprefiion  of  the  brain  induces  deep 
has  not  been  explained,  but  probably  by  diminifhing  the  fecre- 
tion  of  fenforial  power,  and  then  the  voluntary  motions  be- 
come fufpended  previoudy  to  the  irritative  ones,  as  occurs  in 
moll  dying  perfons. 

Another  way  of  procuring  deep  mechanically  was  related  to 
me  by  Mr.Brindley,  the  famous  canal  engineer,  who  was  brought 
up  to  the  bufinefs  of  a mill- wright ; he  told  me,  that  he  had  more 
than  once  feen  the  experiment  of  a man  extending  himfelf  a- 
crofs  the  large  flone  of  a corn-mill,  and  that  by  gradually  let- 
ting the  ftone  whirl,  the  man  fell  afleep  before  the  ftone  had 
gained  its  full  velocity,  and  he  fuppofed  would  have  died  with- 
out pain  by  the  continuance  or  increafe  of  the  motion.  In  this 
cafe  the  centrifugal  motion  of  the  head  and  feet  muft  accumu- 
late the  blood  in  both  thefe  extremities  of  the  body,  and  thus 
comprefs  the  brain. 

Laftly,  we  flrould  mention  the  application  of  cold;  which, 
when  in  a lefs  degree,  produces  watchfulnefs,  by  the  painitocca-  «» 
fions,  and  the  tremulous  convulfions  of  the  fubcutaneous  mpf- 
cles ; but  when  it  is  applied  in  great  degree,  is  laid  to  produce 
deep.  To  explain  this  effcdt  it  has  been  faid,  that  as  the  vef- 
fels  of  the  fkin  and  extremities  become  firfl:  torpid  by  the  -want 
of  the  ftimulus  of  heat,  and  as  thence  lefs  blood  is  circulated 
through  them,  as  appears  from  their  palenefs,  a greater  quantity 


i6o 


OF  REVERIE. 


Sect.  XIX..  i. 


of  blood  poured  upon  the  brain  produces  fleep  by  its  compref- 
fion  of  that  organ.  But  I fhould  rather  imagine,  that  the  fen- 
forial  power  becomes  exhaufted  by  the  convulfive  actions  in 
confequence  of  the  pain  of  cold,  and  of  the  voluntary  exercife 
previoufly  ufed  to  prevent  it ; and  that  the  lleep  is  only  the  be- 
ginning to  die,  as  the  fufpenhon  of  voluntary  power  in  linger- 
ing deaths  precedes  for  many  horns  the  extinction  of  the  irrita- 
tive motions. 

2 1.  The  following  are  the  characleriftic  circumftances  at- 
tending perfect  lleep. 

1.  The  power  of  volition  is  totally  fufpended. 

2.  The  trains  of  ideas  caufed  by  fenfation  proceed  with  grea- 
ter facility  ana  vivacity  ; but  become  inconliftent  with  the  ulua! 
order  of  nature.  The  muibular  motions  caufed  bv  fenfation 
continue  ; as  thofe  concerned  in  our  evacuations  during  infan- 
cy, and  afterwards  in  digeltion,  and  in  priapifmus. 

3.  The  irritative  muicular  motions  continue,  as  thofe  con- 
cerned in  the  circulation,  in  fecretion,  in  refpiration.  But  the 
irritative  fenfual  motions  or  ideas  are  not  excited  ; as  the  imme- 
diate organs  of  lenfe  are'not  himulated  into  adfion  bv  external 
objects,  which  are  excluded  by  the  external  organs  of  fenfe  ; 
which  are  not  in  fleep  adapted  to  their  reception  by  tire  power 
of  volition,  as  in  our  waking  hours. 

4.  The  affociate  motions  continue  ; but  their  hrft  link  is 
not  excited  into  aclion  by  volition,  or  by  external  lfimuli.  In 
all  refpedts,  except  thofe  above  mentioned,  the  three  lalt  fenfo- 
rial  powers  are  fomewhat  increafed  in  energy  during  the  iuf- 
penfion  of  volition,  owing  to  the  confequent  accumulation  c: 
the  fpirit  of  animation. 


SECT.  XIX. 

OF  REVERIE. 

I.  Various  degrees  of  reverie.  2.  Sleep-walkers.  Cafe  of  a 
young  lady.  Great  furprife  at  awaking.  And  total  for- 
getfulnefs  of  what  paffed  in  reverie.  3.  No  fufpenfion 
of  volition  in  reverie.  4.  Senftive  motions  continue , and 
are  conffent.  5.  Irritative  motions  continue , but  are  no: 
fucceeded  by  fenfation.  6.  f ohticn  ncceffary  for  the  per- 
ception of  feeble  impreffions.  7.  Affociated  motions  con- 
tinue. 8.  Nerves  of  fenfe  arc  irritable  in  feep,  but  not 
in  reverie.  9.  Somnambuli  are  not  afeep.  Contagion 
received  but  once.  10.  Definition  of  reverie. 

1.  WHEN  we  are  employed  with  great  fenfation  of  pleafure, 
or  with  great  efforts  of  volition,  in  die  purfuit  of  fome  intereft- 

ihg 


Sect. XIX. 2\  ' OF  REVjLRIE.  i6z 

ing  train  of  ideas,  we  ceafe  to  be  confcious  of  our  exi  Fence, 
are  inattentive  to  time  and  place,  and  do  not  diftinguifh  this  train 
of  fenfitive  and  voluntary  ideas  from  the  irritative  ones  excited 
by  the  prefence  of  external  objects,  though  our  organs  of  feme 
are  furrounded  with  their  accuftomed  ftimuli,  till  at  length  this 
interefting  train  of  ideas  becomes  exhaufted,  or  the  appulfes  of 
external  objefts  are  applied  with  unufual  violence,  and  we  re- 
turn with  furprife,  or  with  regret,  into  the  common  track  of  life. 
This  is  termed  reverie  or  ftudium. 

In  fome  conftitutions  thefe  reveries  continue  a confiderable 
time,  and  are  not  to  be  removed  without  greater  difficulty,  but 
are  experienced  in  a lefs  degree  by  us  all ; when  we  attend 
earneftly  to  the  ideas  excited  by  volition  or  fenfation,  with  their 
affiociated  connections,  but  are  at  the  fame  time  confcious  at 
intervals  of  the  ftimuli  of  furrounding  bodies.  Thus,  in  being 
prefent  at  a play,  or  in  reading  a romance,  fome  perfons  are  fo 
totally  abforbed  as  to  forget  their  ufual  time  of  fleep,  and  to 
neglcCt  their  meals ; while  others  are  faid  to  have  been  fo  in- 
volved in  voluntary  ftudy,  as  not  to  have  heard  jjre  difcharge  of 
artillery  ; and  there  is  a ftory  of  an  Italian  politician,  who 
could  think  fo  intenfely  on  other  fubjecls,  as  to  be  infenfible 
to  the  torture  of  the  rack. 

From  hence  it  appears,  that  thefe  catenations  of  ideas  and 
mufcular  motions,  which  form  the  trains  of  reverie,  are  com- 
poled  both  of  voluntary  and  fenfitive  affociations  of  them ; and 
that  thefe  ideas  differ  from  thofe  of  delirium  or  of  fleep,  as  they 
are  kept  confident  by  the  power  of  volition ; and  they  differ 
alfo  from  the  trains  of  ideas  belonging  to  infanity,  as  they  are 
as  frequently  excited  by  fenfation  as  by  volition.  Eut  laftly, 
that  the  whole  fenforial  power  is  fo  employed  on  thefe  trains 
of  complete  reverie,  that,  like  the  violent  efforts  of  volition,  as 
in  convulffons  or  infanity,  or  like  the  great  adfivity  of  the  ir- 
ritative motions  in  drunkennefs,  or  of  the  fenfitive  motions  in 
delirium,  they  preclude  all  fenfation  confequent  to  external 
ftimulus. 

2.  Thofe  perfons  who  are  faid  to  walk  in  their  fleep,  are 
affedted  with  reverie  to  fo  great  a degree,  that  it  becomes  a 
formidable  difeafe ; the  effence  of  which  conflfts  in  the  inapti- 
tude of  the  mind  to  attend  to  external  ftimuli.  Many  hifto- 
ries  of  this  difeafe  have  been  publiflhed  by  medical  writers  ; of 
which  there  is  a very  curious  one  in  the  Laulanne  Tranf- 
aflions.  I fhall  here  fubjoin  an  account  of  fuch  a cafe,  with 
its  cure,  for  the  better  illuftration  of  this  fubjeCl. 

A very  ingenious  and  elegant  young  lady,  with  light  eyes  ana 
hair,  about  the  age  of  feventeen,  in  other  refpeCts  well,  was  fud- 

denly 


OF  REVERIE. 


Sect.  XIX.  2. 


162 


denly  feized,  foon  after  her  ufual  menftruation,  with  this  very 
wonderful  malady.  The  difeafe  began  with  vehement  convul- 
sions of  almoft  every  mufcle  of  her  body,  widi  great  but  vain 
efforts  to  vomit,  and  the  mod  violent  hiccoughs,  that  can  be 
conceived:  thefe  were  fucceeded  in  about  an  hour  with  a fixed 
fpafm;  in  which  one  hand  was  applied  to  her  head,  and  the 
other  to  fupport  it : in  about  half  an  hour  thefe  ceafed,  and  the 
reverie  began  fuddenly,  and  was  at  firft  manifeft  by  the  look  of 
her  eyes  and  countenance,  which  feemed  to  exprefs  attention. — 
Then  fhe  converfed  aloud  with  imaginary  perfons,  with  her  eyes 
open,  and  could  not,  for  about  an  hour,  be  brought  to  attend  to 
the  Hamulus  of  external  objects  by  any  kind  of  violence,  which 
it  was  proper  to  ufe : thefe  fymptoms  returned  in  this  order  eve* 
ry  day  for  five  or  fix  weeks. 

Thefe  converfations  were  quite  confiftent,  and  we  could  un- 
derftand  what  fhe  fuppofed  her  imaginary  companions  to  an- 
fwer,  by  the  continuation  of  her  part  of  the  difcourfe.  Some- 
times fhe  was  angry,  at  other  times  fhewed  much  wit  and  viva- 
city, but  was  moil  frequently  inclined  to  melancholy.  In  thefe 
reveries  fhe  fometimes  lung  over  lome  mufic  widi  accuracy,  and 
repeated  whole  pages  from  the  Englilh  poets.  In  repeating  fome 
lines  from  Mr.  Pope’s  works,  file  had  forgot  011c  word,  and  be- 
gan again,  endeavouring  to  reGolledlit  ■,  when  fhe  came  to  the 
forgotten  word,  it  was  fhouted  aloud  in  her  ear,  and  this  repeat- 
edly, to  no  purpofe  ; but  by  many  trials  fhe  at  length  regained 
it  herfelf. 

Thefe  paroxyfms  were  terminated  with  the  appearance  of 
inexprefiible  lurprife,  and  great  fear,  from  which  fhe  was  lome 
minutes  in  recovering  herfelf,  calling  on  her  filler  with  great 
agitation,  and  very  frequently  underwent  a repetition  of  con- 
vulfions,  apparantly  from  the  pain  of  fear.  See  Sect.  XVII. 


3-7- 

After  having  thus  returned,  for  about  an  hour  every  day,  for 
two  or  three  weeks,  the  reveries  feemed  to  become  lefs  com- 
plete, and  fome  of  their  circumftances  varied  ; fo  that  fhe  could 
walk  about  the  room  in  them  without  running  againfl  any  of 
the  furniture , though  thefe  motions  were  at  firft  very  unlleady 
and  tottering.  And  afterwards  fhe  once  drank  a dilh  of  tea, 
when  the  whole  apparatus  of  the  tea-table  was  fet  before  her, 
and  expreffed  fome  lufpicion,  that  a medicine  was  put  into  it  ; 
and  once  feemed  to  fmell  to  a tuberofe,  which  was  in  flower  in 
hei  chamber,  and  deliberated  aloud  about  breaking  it  from  the 
ftem,  faying,  “ it  would  make  her  lifter  fo  charmingly  angry.” 
At  another  time. in  her  melancholy  moments  fhe  heard  the  found 
of  a paffuig  bell;  “I  wilh  I was  dead,”  fhe  cried,  liftening  *o 

the 


Sect.  XIX.  3, 4, 5, 6.  OF  REVERIE.  163 

the  bell ; and  then  taking  off  one  ol  her  fhoes,  as  {he  fat  upon  the 
bed,  “ I love  the  colour  black,”  fays  Ihe,  “ a little  wider  and  a 
little  longer,  even  this  might  make  me  a coffin!” — Yet  it  is 
evident  Ihe  was  not  fenfibie  at  this  time,  any  more  than  former- 
ly, of  feeimg  or  hearing  any  perfon  about  her;  indeed,  when 
great  light  was  thrown  upon  her,  by  opening  the  fhutters  of  the 
window,  her  trains  of  ideas  feemed  lefs  melancholy ; and  when 
J have  forcibly  held  her  hands,  or  covered  her  eyes,  {he  appear- 
ed to  grow  impatient,  and  would  fay,  Ihe  could  not  tell  what 
to  do,  for  Ihe  could  neither  fee  nor  move.  In  all  thefe  circum- 
flances  her  pulfe  continued  unaffected  as  in  health.  And  when 
the  paroxyfm  was  over,  me  could  never  recollect  a Angle  idea 
of  what  had  palled  in  it. 

This  aftoni  Idling  difeafe,  after  the  ufe  of  many  other  medicines 
and  applications  in  vain,  was  cured  by  very  large  dofes  of  opi- 
um, given  about  an  hour  before  the  expected  returns  of  the  pa- 
roxyfms  ; and  after  a few  relapfes,  at  the  intervals  of  three  or 
four  months,  entirely  difappeared.  But  {he  continued  at  times, 
to  have  other  fymptoms  of  epilepfy. 

3.  We  thall  only  here  conlider  what  happened  during  the  time 
of  her  reveries,  as  that  is  our  prefent  fubjecSt ; the  fits  of  convul- 
fion  belong  to  another  part 'of  this  treatife.  Sedt.  XXXIV.  44. 

There  feems  to  have  been  no  fufpenfion  of  volition  during 
the  fits  of  reveries,  becaufe  {he  endeavoured  to  regain  the  loft 
idea  in  repeating  the  lines  of  poetry,  and  deliberated  about  break- 
ing the  tubercle,  and  fufpedted  the  tea  to  have  "been  medicated. 

4.  The  ideas  and  mufcular  movements  depending  on  fenfa- 
tioii  were  exerted  with  their  ufual  vivacity,  and  were  kept  from 
being  inconfiftent  by  the  power  ox  volition,  as  appeared  from 
her  whole  converfation,  and  was  explained  in  Seek  XVII.  3.  7. 
and  XVIII.  16. 

5.  The  ideas  and  motions  dependant  on  irritation  during  the 
firft  weeks  of  her  difeafe,  wbilft  the  reverie  was  complete,  were 
never  fucceeded  by  the  fenfation  of  pleafure  or  pain  , as  Ihe 
neither  faw,  heard,  nor  felt  any  of  the  furrounding  objeefs. — 
Nor  was  it  certain  that  any  irritative  motions  fucceeded  the  fti- 
rnulus  of  external  objedfs,  till  the  reverie  became  lefs- complete, 
and  then  {he  could  walk  about  the  room  without  running  a- 
gamft  the  furniture  of  it.  Afterwards,  when  the  reverie  be- 
came frill  lefs  complete  from  the  ufe  of  opium,  fome  few  irri- 
tations were  at  times  fucceeded  by  her  attention  to  them.  As 
when  file  fine] t at  a tuberofe,  and  drank  a dilh  of  tea  ; but  this 
only  when  fhe  leemed  voluntarily  to  attend  to  them. 

6.  In  common  life,  when  we  liften  to  diftant  founds,  or  wifh 
to  diftinguifh  objedfs  in  the  night,  we  are  obliged  ftrongly  to  ex- 

Z ert 


OF  REVERIE. 


Sect.  XIX.  7, 3; 


ert  our  volitisn  to  dipofe  the  organs  of  fenfe  to  perceive  them, 
and  to  fupprefs  the  other  trains  of  ideas,  which  might  interrupt 
thefe  feeble  fenfations.  Hence,  in  the  prefent  hiftory  the  ftrong- 
eft  ftimuli  were  not  perceived,  except  when  the  faculty  of  vo- 
lition was  exerted  on  the  organ  of  fenfe ; and  then  even  com- 
mon ftimuli  were  fometimes  perceived  : for  her  mind  was  fo 
ftrenuoufly  employed  in  purfuing  its  own  trains  of  voluntary  or 
fenfitive  ideas,  that  no  common  ftimuli  could  fo  far  excite  her 
attention  as'  to  difunite  them  ; that  is,  the  quantity  of  volition 
or  of  fenfation  already  exifting,  was  greater  dian  any  which 
could  be  produced  in  confequence  of  common  degrees  of  ftimu- 
lation.  But  the  few  ftimuli  of  the  tuberofe,  and  of  the  tea, 
which  die  did  perceive,  were  fuch,  as  accidentally  coincided 
with  the  trains  of  thought  which  were  palling  in  her  mind  ; 
and  hence  did  not  difunite  thofe  trains,  and  create  furprife. — 
And  their  being  perceived  at  all  was  owing  to  the  power  of  vo- 
lition preceding  or  coinciding  with  that  of  irritation. 

This  explication  is  countenanced  by  a-  facf  mentioned  con- 
cerning a fomnambulift  in  the  Laufanne  Tranfaclions,  who 
fometimes  opened  his  eyes  for  a fhort  time,  to  examine  where 
he  was,  or  where  his  inkpot  ftood,  and  then  fhut  diem  again, 
dipping  his  pen  into  the  pot  every  now  and  then,  and  writing  on, 
but  never  opening  his  eyes  afterwards,  although  he  wrote  on 
from  line  to  line  regularly,  and  corrected  fomeerrors  ot  the  pc:i, 
or  in  fpelling:  fo  much  eafier  was  it  to  him  to  refer  to  his  ideas 
of  the  petitions' of  things,  than  to  his  perceptions  of  them. 

7.  The  aflociated  motions  perfifted  in  their  ufual  channel,  as 
appeared  by  die  combinations  of  her  ideas,  and  the  ufe  of  her 
nlufcles,  and  the  equality  of  her  pulfe ; for  the  natural  motions 
of  the  arterial  fyftem,  though  originally  excited  like  other  mo- 
tions by  ftimulus,  feem  in  part  to  continue  by  their  affociation 
with  each  other.  As  the  heart  of  a viper  pull'ates  long  after 
it  is  cut  out  of  the  body,  and  removed  from  the  ftimulus  of  the 
Blood. 


8.  In  the  fedfion  on  lleep  it  was  obferved  that  the  nerves  ot 
fenfe  are  equally  alive  and  fufceptible  to  irritation  in  that  ftate, 
as  when  we  are  awake ; but  that  they  are  fecluded  from  ftimu- 
lating  objedts,  or,  rendered  unfit  to  receive  them  : but  in  com- 
plete reverie  the  reverfe  happens,  the  immediate  organs  of  fenfe 
are  expofed  to  their  ufual  ftimuli ; but  are  either  not  excited 
into  adfion  at  all,  or  not  into  fo  great  adfion  as  to  produce  at- 
tention or  fenfation. 

The  total  torgetfulnefs  of  what  pafles  in  reveries ; and  the 
furprife  on  recovering  from  them,  are  explained  in  Sedfion 
XVIII.  19.  and  in  Section  XVII.  3.  7. 

9.  It 


OF  VERTIGO. 


SreT.XX. 


9.  It  appears  from  hence,  th-at  reverie  is  a difeafe  of  the  epi- 
leptic orcateleptic  kind,  lince  the  paroxyfms  of  this  young  lady 
always  began  and  frequently  terminated  with  convulfions ; and 
■though  in  its  greateft  degree  it  has  been  called  fomnambulation, 
or  fleep-walking,  it  is  totally  different  from  lleep ; becaufe  the 
eflential  character  of  fleep  confifts  in  the  total  fufpenfion  of  vo- 
lition, which  in  reverie  is  not  affedted ; and  the^effential  cha- 
racter of  reverie  confifts  not  in  the  abfence  of  thofe  irritative 
.motions  of  our  fenfes,  which  are  occafioned  by  the  ftimulus  of 
external  objects,  but  in  their  never  being  productive  of  fenfation. 
So  that  during  a fit  of  reverie  that  Arrange  event  happens  to  the 
whole  fyftem  of.nerves,  which  occurs  only  to  fome  particular 
branches  of  them  in.  thofe  who  are  a fecond  time  expofed  to  the 
.action  of  contagious  matter.  If  the  matter  of  the  fmall-pox 
be  inferted  into  the  arm  of  one  who  has  previo-ufly  had  that  di- 
feafe, it  will  ftimulate  the  wound ; but  the  general  fenfation  or 
-inflammation  of  the  fyftem  does  not  follow,  which  conftitutes 
.the  difeafe.  See  Seft'.  Xlf  7.  6.  XXXIII.  a.  8. 

10.  The  following  is  the  definition,  or  character,  of  complete 
.reverie.  1.  The  irritative  motions  occafioned  by  internal  fti- 
• muli  continue ; thofe  from  the  ftimuli  of  external  objects  are  ei- 
ther not  produced  at  all,  or  are  never  fucceeded  by  fenfation  or 
.attention,  unlefs  they  are  at  the  fame  time  excited  by  -volition. 

2.  The  fenfitive  motions  continue,  and  are  kept  confident  by 
.the  power  of  volition.  3.  The  voluntary  motionscontinue  un- 
.difturbed.  4.  The  affociate  motions  continue  undifturbed. 

Two  other  cafes  of  reverie  are  related  in  Sedition  XXXIV. 

3.  which  further  evince,  that  reverie  is  an  effort  of  the  mind, 
4°  relieve  fome  painful  fenfation,  and  is  hence  allied  to  con- 
vulfion,  and  to  infanity. 


SECT.  XX. 

OF  VERTIGO. 

4t.  We  determine  our  perpendicularity  by  the  apparent  mo- 
tions ef  objects.  A perfon  hood-winked  cannot  walk  in  a 
JLraight  line.  Dizzinefs  on  looking  from  a tower,  in  a 
room  Jlained  with  uniform  lozenges , on  riding  over  fnow . 
2.  Dizzinefs  from  moving  objects.  A whirling  wheel. 
Fluctuations  of  a river.  Experiment  with  a child.  3. 
Dizzinefs  from  our  own  motions  and  thofe  of  other  ob- 
jects. Riding  over  a broad  flream.  Sea-fcknefs.  5.  Of 
turning  round,  on  one  foot.  Dervifes  in  Turkey.  At- 
tention cf  the  mind  prevents  fight  fca-ficknefs.  After  a 

voyage 


OF  VERTIGO. 


Sect.  XX.  i 


t 66 

voyage  ideas  of  vibratory  motions  are  f ill  perceived  on 
fiorc.  6.  Ideas  continue  Jome  time  after  they  are  excited, 
a rcumfances  of  turning,  on  one  foot  ,fianding  on  a tower, 
and  vjaiking  in  the  dark  explained.  7.  Irritative  ideas 
of  apparent  motions.  Irritative  ideas  of  founds.  Bat  le- 
nient of  the  found  of  bells  and  organ-pipes.  Vertiginous 
noife  in  the  head.  Irritative  motions  of  the  fornach , in- 
iefiines,  and  glands.  8.  Symptoms  that  accompany  verti- 
go. Why  vomiting  comes  on  in  firokes  of  the  pal  fey.  By 
the  'motion  of  a flip.  By  injuries  on  the  head.  Why  mo- 
tion makes  fick  people  Vomit.  9.  Why  drunken  people  arc 
vertiginous.  Why  a fone  in  the  ureter,  or  bile-duel,  pro- 
duces vomiting.  IO.  Why  after  a voyage  ideas  of  vi- 
bratory motions  are  perceived  on  fiorc.  11.  Kinds  of  ver- 
tigo and  their  cure.  12.  Definition  of  vertigo. 

1.  IN  learning  to  walk,  we  judge  of  die  diftances  of  the 
objects  which  we  approach,  bv  the  eye:  and  by  obferving 
their  perpendicularity  determine  our  own.  This  circumftance 
not  having  been  attended  to  by  the  writers  on  vilion,  the  dil- 
eafe  called  vertigo,  or  dizzinefs,  has  been  little  underftood. 

When  any  perfon  lofes  the  power  of  mufeuiar  action,  whe- 
ther he  is  erect,  or  in  a fitting  pofture,  he  links  down  upon  the 
ground;  as  is  feen  in  fainting  fits,  and  other  inftances  of  great 
debility.  Hence  it  follows,  that  fome  exertion  of  mufeuiar 
power  is  neceffary  to  preferve  our  perpendicular  attitude.  This 
is  performed  by  proportionally  exerting  the  antagonift  rouf- 
cles  of  the  trunk,  neck,  and  limbs;  and  if  at  anv  time  in  our 
locomotions,  we  find  ourlelves  inclining  to  one  tide,  we  either 
reftore  our  equilibrium  by  the  efforts  of  the  mufcles  on  the 
other  fide,  or  by  moving  one  of  our  feet,  extend  the  bale, 
which  we  reft  upon,  to  the  new  centre  of  gravity. 

But  the  moft  eafy  and  habitual  manner  of  determining  our 
want  of  perpendicularitv,  is  by  attending  to  the  apparent  mo- 
tion of  the  objedls  within  the  fphere  of  diftindl  vilion  ; for 
this  apparent  motion  of  objects,  when  we  incline  from  cur 
perpendicularity,  or  begin  to  fall,  is  as  much  greater  than  the 
real  motion  of  the  eye,  as  the  diameter  of  the  fphere  of  dif- 
tindb  vifion  is  to  cur  perpendicular  height. 

Hence,  no  one  who  is  hood-winked,  can  walk  in  a ftraight 
line  for  a hundred  fteps  together;  for  he  inclines  fo  greatly, 
before  he  is  warned  ot  his  want  of  perpendicularitv  by  the  fenie 
of  touch,  not  having  the  apparent  motions  of  ambient  ob- 
jects to  meafure  this  inclination  by,  that  he  is  neceflitafed  to. 
move  one  of  his  feet  outwards,  to  tire  right  or  to  the  left,  to 

fupport 


OF  VERTIGO. 


Sect.  XX.  2, 3. 


167 


fupport  the  new  centre  of  gravity,  and  thus  errs  from  the  line 
he  endeavours  to  proceed  in. 

For  the  fame  reafon  many  people  become  dizzy,  when  they 
l-ook  from  the  fummit  of  a tower,  which  is  raifed  much  above 
all  other  objeds,  as  thefe  objects  are  out  of  the  fphere  of  dif- 
finct  viiion,  and  they  are  obliged  to  balance  their  bodies  by  the 
lefs  accurate  feelings  of  their  mufcles. 

There  is  another  curious  phenomenon  belonging  to  this 
place,  if  the  circumjacent  vifible  objeds  are  fo  fmall,  that  we 
do  not  diftinguifh  their  minute  parts  ; or  fo  fimilar,  that  we 
do  not  know  them  from  each  other,  we  cannot  determine  our 
perpendicularity  by  them.  Thus,  in  a room  hung  with  a pa- 
per which  is  coloured  over  with  fimilar  fmall  black  lozenges 
or  rhomboids,  many  people  become  dizzy  ; for  when  they  be- 
gin to  fall,  the  next,  and  the  next  lozenge  fucceeds  upon  the 
eye ; which  they  mi  {lake  for  the  firft,  and  are  not  aware  that 
they  have  any  apparent  motion.  Eut  if  you  fix  a fiieet  of  pa- 
per, or  draw  any  other  figure,  in  the  mid  ft  of  thefe  lozenges, 
the  charm  ceaies,  and  no  dizzinefs  is  perceptible.  The  fame 
occurs  when  we  ride  over  a plain  covered  with  fnow,  with- 
out trees  or  other  eminent  objedcs. 

2.  But  after  having  compared  vifible  objeds  at  reft  with  the 
fenfe  of  touch,  and  learnt  to  diftinguifh  their  fliapes  and  fhades, 
and  to  meafure  our  want  of  perpendicularity  by  their  apparent 
motions,  we  come  to  confider  them  in  real  motion.  Here  a 
new  difficulty  occurs,  and  we  require  feme  experience  to  learn 
the  peculiar  mode  of  motion  of  any  moving  objeds,  before  we 
can  make  ufe  of  them  for  the  purpofes  of  determining  cur  per- 
pendicularity. Thus  fome  people  become  dizzy  at  the  light  of 
a whirling  wheel,  or  by  gazing  on  the  fluduations  of  a river, 
if  no  fteady  objeds  are  at  the  fame  time  within  the  fphere  of 
their  diftind  vifion  ; and  when  a child  firft  can  ftand  ered 
upon  his  legs,  if  you  gain  his  attention  to  a white  handkerchief 
fteadily  extended  like  a fail,  and  afterwards  make  it  undulate, 
he  inftantly  lofes  his  prependicularity,  and  tumbles  on  the 
ground. 

3.  A fecond  difficulty  we  have  to  encounter  is  to  diftinguifh 
our  own  real  movements  from  the  apparent  motions  of  ob- 
jeds. Our  daily  pradice  of  walking  and  riding  on  horfeback, 
foon  inftruds  us,  with  accuracy,  to  difeern  thefe  modes  of  mo- 
tion, and  to  aferibe  the  apparent  motions  of  the  ambient  ob- 
jeds to  ourfelves ; but  thofe  which  we  have  not  acquired  by- 
repeated  habit,  continue  to  confound  us.  So,  as  we  ride  on 
horfeback,  the  trees  and  cottages  which  occur  to  us  appear 
at  reft  ; we  can  meafure  their  diftances  with  our  eye,  and  re- 
gulate 


* 

* 


OF  VERTIGO. 


£08 


Sect.  XX.  4,  5. 


f-alate  our  attitude  by  them;  yet  if  we  carelefsly  attend  to  dis- 
tant hills  or  woods,  through  a thin  hedge,  which  is  near  us, 
we  obfervc  the  jumping  and  progreffive  motions  of  them  ; as 
this  is  increafedby  the  paratax  ofthefe  objects,  which  we  have 
not  habituated  Qurfelves  to  attend  to.  When  lirfb  an  Euro- 
pean mounts  an  elephant  frxteen  feet  high,  and  whofe  mode  of 
motion  he  is  not  accullomed  to,  the  objedbs  feem  to  undulate 
as  he  paflfes,  and  he  frequently  becomes  lick  and  vertiginous, 
as  I am  well  informed.  Any  other  unufual  movement  of  our 
bodies  has  the  fame  effedf,  as  riding  backwards  in  a coach, 
f winging  on  a rope,  turning  round  fwiftlv  on  one  leg,  fearing 
on  the  ice,  and  a thoufand  others.  So,  after  a patient  has  been 
•long  confined  to  his  bed,  when  he  firft  attempts  to  walk,  he 
finds  himfe-lf  .vertiginous,  and  is  obliged,  by  practice,  to  learn 
again  the  particular  modes  of  the  apparent  motions  of  objects, 
as  he  walks  by  them. 

4.  A third  difficulty  which  occurs  to  us  in  learning  to  ba- 
lance ourielv.es  by  the  eye,  is,  when  both  ourfelves  and  the  cir- 
cumjacent objects  are  in  real  motion.  Here  it  is  neceffiarv, 
that  we  fliould  be  habituated  to  both  thefe  modes  of  motion  in 
order  to  preferve  our  perpendicularity.  Thus,  on  horfeback. 
we  accurately  obferve  another  perfon,  whom  we  meet  trotting 
towards  us,  without  confounding  his  jumping  and  progreffive 
motion  with  our  own,  becaufe  we  have  been  aecuftomed  to 
them  both ; that  is,  to  undergo  the  one,  and  to  fee  the  other  at 
the  fame  time.  Rut  in  riding  over  a broad  and  flu&uating 
itream,  though  we  are  well  experienced  in  the  motions  of  our 
horfe,  we  are  liable  to  become  dizzy  from  our  experience  in 
that  of  the  water.  And  when  tirft  we  go  on  {hip-board,  where 
che  movements  of  ourfelves,  and  the  movements  of  tire  large 
waves  are  both  new  to  us,  the  vertigo  is  almoft  unavoidable 
with  the  terrible  licknefs  which  attends  it.  And  this  I have 
been  allured  has  happened  to  feveral  from  being  removed  from 
a large  (hip  into  a (mall  one ; and  again,  from  a fmall  one 
into  a man  ot  ‘war. 

5.  From  the  foregoing  examples  it  is  evident,  that  whet) 
we  are  furrounded  with  unulpal  motions,  we  lofe  our  perpen- 
dicularity: but  there  are  fome  peculiar  circumftances  attend- 
ing this  effedt  of  moving  objects,  which  we  come  now  to 
mention,  and  {hall  hope,  from  the  recital  of  them,  to  gain  fome 
infight  into  the  manner  of  their  production. 

When  a child  moves  round  quick  upon  one  foot,  the  cir- 
cumjacent objects  become  quite  indiftindfc,  as  their  diftance 
increafes  their  apparent  motions ; and  this  great  velocity  con- 
founds both  their  forms  and  their  colours,  as  is  feen  in  whirl- 
ing 


Sect.  XX.  6. 


of  vertigo:  i 69 

mg  round  a many  coloured  wheel ; he  then  lofes  his  ufual 
method  of  balancing  himfelf  by  vihon,  and  begins  to  flagger, 
and  attempts  to  recover  himfelf  by  his  mufcular  feelings.  This 
daggering  adds  to  the  inftability  of  the  vilibie  objects,  by  giving 
a vibratory  motion  befides  their  rotatory  one.  The  child  then- 
drops  upon  the  ground,  and  the  neighbouring  objeds  feem  to 
continue  for  fome  feconds  of  time  to  circulate  around  him,  and 
the  earth  under  him  appears  to  librate  like  a balance.  In  fome 
feconds  of  time  thefe  fenfations  of  a continuation  of  the  motion 
of  objeds  vanifh  ; but  if  he  continues  turning  round  fome- 
what  longer,  before*  he  falls,  dckneis  and  vomiting  are  very 
liable  to  lucceed.  But  none  of  thefe  circumftances  affect  thole 
who  have  habituated  themfelves  to  this  kind  of  motion,  as  the 
dervifes  in  Turkey,  among!!  whom  thefe  fwift  gyrations  are  a 
ceremony  of  religion.. 

In  an  open  boat  palling  from  Leith  to  Kinghorn,  in  Scot- 
land, a fudden  change  of  the  wind  ihook  the  undiftended  fail, 
and  ftopt  ©ur  boat:  from  this  unufual  movement  the  paflenger:* 
all  vomited  except  myfelf.  I obferved  that  the  undulation  of 
the  fhip,  and  the  inftability  of  all  vilibie  objects,  inclined  me 
ftrongly  to  be  fick  and  this  continued,  or  increafed,  when- 1 
clofed  my  eyes,  but  as  often  as  I bent  my  attention  with  energy 
on  the  management  and  mechanifm  of  the  ropes  and  fails,  the 
ficknefs  ceafed,  and  recurred  again  as  often  as  I relaxed  this 
attention ; and  I am  allured,  by  a gentleman  ol  obfervation  and 
veracity,  that  he  has  more  than  once  obferved,  when  the  vef- 
fel  has  been  in  immediate  danger,  that  the  fea-hcknefs  of  die 
paflengers  has  inftantaneoully  ceafed,  and  recurred  again 
when  the  danger  was  over. 

Thofe  who  have  been  upon  the  water,  in  a boat  or  fhip,  fo 
long  that  they  have  acquired  the  ne-celfary  habits  of  motion 
upon  diat  unftable  element,  at  their  return  on  land  frequently 
chink,  in  their  reveries,  or  between  deeping  and  waking,  that 
they  obferve  the  room  they  fit  in,  or  lome  of  its  furniture,  to 
librate  like  the  motion  of  the  velTd.  This  I have  experienced 
myfelf,  and  have  been  told,  that  alter  long  voyages  it  is  fome 
time  before  thefe  ideas  entirely  vanifh.  The  fame  is  obiervable 
in  a lefs  degree  after  having  travelled  fome  days  in  a ftage- 
coach,  and  particularly  when  we  lie  down  in  bed,  and  compofe* 
ourfelves  to  deep:  in*  this  cafe* it  is  obfervable  that  the  rattling 
node  of  the  coach,  as  well  as  the  unduiatory  motion,  haunts 
us.  The  drunken  vertigo,  and  the  vulgar  cuftora  of  rocking 
children,  will  be  conddered  in  the  next  Section. 

6.  The  motions  which  are  produced  by  the  power  of  voli- 
tion, may  be  immediately  flopped  by  the  exertion  of  the  fan  e 

power 


I '70 


OF  VERTIGO, 


Sect.  XX.  6: 

power  on  the  antagonift  mufcles,  otherwise  thefe,  with  all  the 
other  clafies  of  motion,  continue  to  go  on  feme  time  after  they 
are  excited,  as  the  palpitation  of  the  heart  continues  after  the 
object!  of  fear,  which  occafioned  it,  is  removed.  But  thin  cir- 
cumibance  is  in  no  clafs  of  motions  more  remarkable  than  in 
thofe  dependent  on  irritation:  thus,  if  any  one  looks  at  the 
fun,  and  then  covers  his  eyes  with  his  hand,  he  will,  for  many 
feconds  of  time,  perceive  the  image  of  the  fun  marked  on  his 
retina:  a limilar  image  of  all  other  viiible  objects  would  re- 
main fome  time  formed  on  the  retina,  but  is  extinguifhed  by 
the  perpetual  change  of  the  motions  of  this  nerve  in  our  atten- 
tion to  other  objects.  To  this  muft  be  added,  that  the  longer 
time  any  movements  have  continued  to  be  excited  without  fa- 
tigue to  the  organ,  the  longer  will  they  continue  fpontaneoul- 
ly,  after  the  excitement  is  withdrawn : as  the  tafle  of  tobacco 
in  the  mouth. alter  a perfon  has  been  fmoaking  it.  This  tafle 
remains  fo  ftrong,  that  if  a perfon  continues  to  draw  air  through 
a tobacco  pipe  in  the  dark,  after  having  been  fmoaking  fome 
time,  he  cannot  diftinguifh  whether  his  pipe  be  lighted  or  not. 

From  thefe  two  confiderations  it  appears,  that  the  dizzinefs 
felt  in  the  head,  after  feeing  objedls  in  unufua!  motion,  is  no 
other  than  a continuation  of  the  motions  of  the  optic  nerve, 
excited  by  thofe  objects,  and  which  engage  our  attention. 
Thus,  on  turning  round  on  one  foot,  the  vertigo  continues  for 
fome  feconds  of  time  after  the  perfon  is  fallen  on  the  ground ; 
and  the  longer  he  has  continued  to  revolve,  the  longer  will  con- 
tinue thefe  fucceffive  motions  of  the  parts  of  the  optic  nerve. 

After  revolving,  with  your  eyes  open,  till  you  become  verti- 
ginous, as  foon  as  you  ceafe  to  revolve,  not  only  the  circum- 
ambient objedls  appear  to  circulate  round  you  in  a direction 
contrary  to  that  in  which  you  have  been  turning,  but  you  arc 
liable  to  roll  your  eyes  forwards  and  backwards,  as  is  well  ob- 
ferved,  and  ingenioufly  demonflrated  by  Dr.  Wells  in  a late 
publication  on  vifion.  The  fame  occurs,  it  you  revolve  with 
your  eyes  clofed,  and  open  them  immediately  at  the  rime  ot  vour 
ceafingto  turn  ; and  even  during  the  whole  time  of  revolving, 
as  may  be  felt  by  your  hand  preiTed  lightly  on  your  clofed  eve- 
lids.  To  thefe  movements  of  the  eyes,  of  which  he  fuppofes  the 
obferver  to  be  inconfcious,  Dr.  Vv  ells  aferibes  die  apparent 
circumgyration  of  objedls  on  ceafing  to  revolve. 

The  caufe  of  thus  turning  our  eyes  forwards,  and  then 
back  again,  after  our  body  is  at  reft,  depends,  I imagine,  on 
the  fame  circumftance  which  induces  us  to  follow  the  indil- 
tindl  fpcdlra  which  are  formed  on  one  fide  of  the  centre  of 
the  retina,  when  we  obferve  diem  apparendv  on  clouds,  as 

delcribed 


Sect.  XX.  6.  OF  VERTIGO.  171 

defcribed  in  Sedt.  XL.  2.  2.  and  then  not  being  able  to  gain 
a more  diftindt  vifion  of  them,  we  turn  our  eyes  back,  and 
again  and  again  purfue  the  flying  {hade. 

But  this  rolling  of  the  eyes,  after  revolving  till  we  become  ver- 
tiginous, cannot  caufe  the  apparent  circumgyration  of  objedts, 
in  a direction  contrary  to  that  in  which  we  have  been  revolving, 
for  the  following  reafons.  1.  Becaufe,  in  purfuing  a fpedtrum 
in  the  fky,  or.  on  the  ground,  as  above-mentioned,  we  perceive 
no  retrograde  motions  of  objedts.  2.  Becaufe  the  apparent 
retrograde  motions  of  objedts,  when  we  have  revolved  till  we 
are  vertiginous,  continues  much  longer  than  the  rolling  of  the 
eyes  above  defcribed. 

3.  When  we  have  revolved  from  right  to  left,  the  apparent 
motion  of  objedts,  when  we  flop,  is  from  left  to  right ; and  when 
we  have  revolved  from  left  to  right,  the  apparent  circulation  of 
objedts  is  from  right  to  left;  yet  in  both  thefe  cafes  the  eyes  of 
the  revolver  are  feen  equally  to  roll  forwards  and  backwards. 

4.  Becaufe  this  rolling  of  the  eyes  backwards  and  forwards 
takes  place  during  our  revolving,  as  may  be  perceived  by  the 
hand  lightly  prefTed  on  the  clofed  eyelids,  and  therefore  exifts 
before  the  effedt  afcribed  to  it. 

And,  fifthly,  I now  come  to  relate  ah  experiment  in  which 
the  rolling  of  the  eyes  does  not  take  place  at  all  after  revolving, 
and  yet  the  vertigo  is  mote  diftreffing  than  in  the  lituations  above 
mentioned.  If  any  one  looks  fteadiiy  at  a fpot  in  the  ceiling 
over  his  head,  or  indeed  at  his  own  finger  held  up  high  over  his 
head,  and  in  that  fituation  turns  round  till  he  becomes  giddy, 
and  then  flops,  and  looks  horizontally,  he  now  finds  that  the 
apparent  rotation  of  objedts  is  from  above  downwards,  or  front 
below  upwards ; that  is,  that  the  apparent  circulation  of  objedts 
is  now  vertical  inftead  of  horizontal,  making  part  of  a circle 
round  the  axis  of  his  eye;  and  fins  without  any  rolling  of  the 
eyeballs.,  The  reafon  of  there  being  no  rolling  of  his  eyeballs 
perceived  after  this  experiment,  is,  becaufe  the  images  of  objedts 
are  formed  in  rotation  round  the  axis  of  the  eye,  and  not  from 
one  fide  to  the  other  of  the  axis  of  it ; fo  that,  as  the  eyeball 
has  not  power  to  turn  in  its  focket  round  its  own  axis,  it  can- 
not follow  the  apparent  motions  of  thefe  evanefeent  fpedtra, 
either  before  or  after  the  '*ody  is  at  reft.  From  all  which  ar- 
guments ic  is  manifeft,  that  thefe  apparent  retrograde  gyra- 
tions of  objedts  are  not  caufed  by  the  rolling  of  the  eyeballs: 
Firft,  becaufe  no  apparent  retrogreffion  of  objedts  is  obferved 
in  other  rollings  of  the  eyes.  Secondly,  becaufe  the  apparent  re- 
trogreffion of  objedts  continues  many  leconds  after  the  rolling 
of  the  eyeballs  ceafes.  Thirdly,  becaufe  the  apparent  retro- 
A a greffioti 


OF  VERTIGO. 


Sect.  XX.  &. 


tjz 

grc-ffion  of  objects  is  fometinaes  one  way,  and  fometimes  ano- 
ther, yet  the  rolling  of  the  eyeballs  is  the  fame.  Fourthly,  be- 
car.fethe  rolling  of  the  eyeballs  exifts  before  the  apparent  re- 
trograde motions  of  otiedts  is  obferved;  that  is,  before  the  re- 
volving perfon  flops.  And,  fifthly,  becaufe  the  apparent  retro- 
grade gyration  of  objects  is  produced,  when  there  is  no  roiling 
of  the  eyeballs  at  ail. 

Doctor  V/eils  imagines,  that  no  fpedlra  can  be  gained  in 
the  eye,  if  a perfon  revolves  with  his  eyelids  clofed ; and  thinks 
this  a fufficient  argument  againfr  the'  opinion,  that  the  appa- 
rent progreffion  or  the  fpedtra  of  light  or  colours  in  fhe  eye, 
can  cauie  the  apparent  retrogreffion  of  objedts  in  the  vertigo 
above  deferibed ; but  it  is  certain,  when  any  perfon  revolves  in 
a light  room  with  his  eyes  clofed,  taint  he  neverthelefs  perceives 
differences  oflliglit  both  in  quantity  and  colour  through  his  eye- 
lids, as  tie  turns  round;  and  readily  gains  fpedtra  of  thofe  dif- 
ferences. And  thefe  fpedtra  are  not  very  different,  except  in 
vivacity,  from  thofe  which  he  acquires  when  he  revolves  with 
unclofed  eyes ; fmee,  il  he  then  revolves  very  rapidly,  die  co- 
lours and  forms  of  furrounding  objects  are,  as  it  were,  mixed 
together  in  his  eye;  as  when  the  prifmatic  colours  are  painted 
on  a wheel,  they  appear  white  as  they  revolve.  The  truth  of 
this  is  evinced  by  the  daggering  or  vertigo  of  men  perfectly 
blind,  when  they  turn  round ; which  is  not  attended  with  ap- 
parent circulation  of  objedts,  but  is  a vertiginous  diforder  of 
the  fenie  of  touch.  Blind  men  balance  themfelves  by  their 
fenfe  of  touch;  which,  being  lefs  adapted  for  perceiving  ftnall 
deviations  from  their  perpendicular,  occafions  them  to  carry 
themfelves  more  eredi,  in  walking.  This  method  of  balancing 
themfelves  by  the  diredtion  of  their  preflure  againft  the  floor, 
becomes  difordered  by  the  unufual  mode  of  adtion  in  turning 
round,  and  they  begin  to  lofe  their  perpendicularity  ; that  is, 
they  become  vertiginous,  but  without  any  apparent  circular 
motions  of  vifible  objedts. 

It  will  appear  from  the  following  experiments,  that  the  ap- 
parent progreffion  of  die  ocular  Ipedtra  of  light  or  colours,  is 
the  cauie  ot  the  apparent  retrogreffion  of  objects,  alter  a p tr- 
io n has  revolved  till  he  is  vertiginous. 

Firft,  when  a perfon  turns  round  in  a light  room  with  his 
eyes  open,  but  doles  them  before  he  Hops,  he  will  feem  to  he 
carried  forwards  in  the  diredtion  he  was  turning  lor  a lhon 
time  after  he  Hops.  But  if  he  opens  his  eyes  again,  the  ob- 
jedts  before  him  inftantly  appear  to  move  in  a retrograde  di- 
redtion, and  he  lol'es  the  fenla.ion  of  being  carried  forwards. 
The  fame  occurs  if  a perfon  rev'olves  in  a light  room  with  his 

eyes 


OF  VERTIGO, 


$ECT.  XX.  6- 


173 


eyes  clofed ; when  he  flops,  he  feems  to  he  for  a time  carried 
forwards,  if  his  eyes  are  ftiil  clofed;  but  the  inftant  he  opens 
them,  the  furrounding  objects  appear  to  move  in  a retrograde 
gyration.  From  hence  it  may  be  concluded,  that  iriis  the  fen- 
iation  or  imagination  of  our  continuing  to  go  forwards  in  the 
direction  in  which  we  were  turning,  that  caufes  the  apparent 
retrograde  circulation  of  objects. 

. Secondly,  though  there  is  an  audable  vertigo,  as  is  known 
by  the  battement,  or  undulations  of  found  in  the  ears,  which 
many  vertiginous  people  experience ; and  though  there  is  alfo  a 
tangible  vertigo,  as  when,  a blind  perfon  turns  round,  as  men- 
tioned above ; yet  as  this  circumgyration  of  objects  is  an  hallu- 
cination or  deception  of  the  fenle  of  fight,  we  are  to  look  for 
tire  caufe  of  our  appearing  to  move  forward,  when  we  flop  with 
our  eyes  clofed  after  gyration,  to  fome  affection  of  this  fenfe. 
Now,  thirdly,  if  the  fpectra  formed  in  the  eye  during  our  rota- 
tion, continue  to  change,  when  we  ftand  ftiil,  like  the  fpectra 
defcribedin  Se£t,  III.  3.  6.  fuch  changes  muft  fuggeft  to  us  the 
idea  or  fenfation  of  our  ftiil  continuing  to  turn  round ; as  is  the 
cafe  when  we  revolve  in  a light  room,  and  dole  our  eyes  be- 
fore we  flop.  And,  laftly,  on  opening  our  eyes  in  the  fituatiort 
above  deferibed,  the  objects,  we  chance  to  view  amid  thefe  chang- 
ing fperitra  in  the  eye,  muft  feem  to  move  in  a contrary  direc- 
tion; as  the  moon  fometimes  appears  to  move  retrograde,  when 
fwift-gliding  clouds  are  paffirtg  forwards  fo  much  nearer  the  eye 
pf’the  beholder. 

To  make  obfervations  on  faint  ocular  fperitra  requires  forne 
degree  of  habit  and  compofure  of  mind,  and  even  patience; 
fome  of  thofe  deferibed  in  Sedt.  XL.  were  found  difficult  to  fee, 
by  many  who  tried  them ; now,  it  happens  that  the  mind,  dur- 
ing the  confufton  of  vertigo,  when  all  the  other  irritative  tribes 
of  motion,  as  well  as  thofe  of  vifton,  are  in  fome  degree  dis- 
turbed, together  with  the  fear  of  falling,  is  in  a very  unfit  ftate 
for  the  contemplation  of  fuch  weak  feniations,  as  are  occailoneu 
by  faint  ocular  fpectra.  Yet  after  frequently  revolving,  both 
with  my  eyes  clofed,  and  with  them  open,  and  attending  to  the 
fpectra  remaining  in  them,  by  ftiading  the  light  from  my  eye- 
lids more  or  lefs  with  my  hand,  I at  length  ceafed  to  have  the 
idea  ot  going  forward,  after  I flopped  with  my  eyes  clofed ;'  and 
law  changing  fpectra  in  my  eyes,  which  feemed  to  move,  as  it 
were,  over  the  held  of  vifton;  till  at  length,  by  repeated  trials 
on  funny  days,  I perfuaded  myfelf,  on  opening  my  eyes,  after 
revolving  fome  time,  on  a fhelf  of  gilded  books  in  my  library, 
that  I could  perceive  the  fpedtra  in  my  eyes  move  forwards  over 
one  cr  two  of  the  books,  like  the  vapours  in  the  air  of  a fum- 

mer’s 


274 


OF  VERTIGO. 


Sect.  XX.  6. 


iner’s  day;  and  could  fo  far  undeceive  myfelf,  as  to  perceive 
the  hooks  to  ftand  ft  ill.  After  more  trials  I fometimes  brought 
myfelf  to  believe  that  1 faw  changing  fpedtra  of  lights  and 
/hades  moving  in  my  eyes,  after  turning  round  for  fome  time, 
but  did  not  imagine  eithei  the  fpedtra  or  the  objedts  to  be  in  a 
ftate  of  gyration.  I fpeak,  however,  with  diffidence  of  thefe 
faffs,  as  I could  not  always  make  the  experiments  fucceed, 
when  there  w7as  not  a ftrong  light  in  my  room,  or  when  my 
eyes  were  not  in  the  moft  proper  ftate  for  fuch  obfervations. 

The  ingenious  and  learned  M.  Savage  has  mentioned  ciher 
theories  to  account  for  the  apparent  circumgyration  of  objedts 
in  vertiginous  people.  As  the  retrograde  motions  cf  the  par- 
ticles of  blood  in  the  optic  arteries,  by  fpafm,  or  by  fear,  as  is 
feen  in  the  tails  of  tadpoles,  and  membranes  between  the  fingers 
of  frogs.  Another  caufe  he  thinks  may  be  from  the  librations 
to  one  fide,  and  to  the  other,  of  tire  cryftalline  lens  in  the  ey®, 
by  means  of  involuntary  adtions  of  the  mufcles,  which  coniii- 
tuce  the  ciliary  procefs.  Both  thefe  theories  lie  under  the  fame 
objection  as  that  of  Dr.  Weils  before-mentioned ; namely,  that 
the  apparent  motions  of  objedts,  after  the  ohferver  has  revolved 
for  lome  time,  fhould  appear  to  vibrate  this  way  and  that;  and 
not  to  circulate  uniformly  in  a direction  contrary  to  that  in 
which  the  obferver  had  revolved. 

M.  Savage  has,  laftly,  mentioned  the  theory  of  colours  left  in 
the  eye,  which  he  has  termed  impreffions  on  the  retina.  He  fays, 
“ Experience  teaches  us,  that  impreffions  made  on  the  retina, 
by  a vifible  object,  remain  fome  feconds  alter  the  objedt  is  re- 
moved ; as  appears  from  the  circle  of  fire  which  we  fee  when  a 
fire-fuck  is  whirled  round  in  the  dark ; therefore,  when  we  are 
carried  round  our  own  axis  in  a circle,  we  undergo  a tem- 
porary vertigo,  when  we  flop;  becaufe  the  impreffions  of  the 
circumjacent  objedts  remain  tor  a time  afterwards  on  the  reti- 
na.” Nofolog.  Method.  Claf.  VIII.  i.  i.  We  have  before 
obferved.  that  the  changes  of  thefe  colours  remaining  in  the  eye, 
evinces  them  to  be  motions  of  the  fine  terminations  of  the  reti- 
na, and  not  impreffions  on  it;  as  impreffions  on  a paffive  lub- 
ftance  muft  either  remain,  or  ceaie  intirely. 

Any  one  who  ftands  alone  on  the  top  of  a high  tosver,  if  lie 
has  not  been  accuftomed  to  balance  himfelf  by  objedts  placed 
at  fuch  diftaiices  and  with  fuch  inclinations,  begins  to  flagger, 
and  endeavours  to  recover  himfelf  by  his  mufcular  feelings. 
During  this  time  the  apparent  motion  of  objedts  at  a diftance 
below  him  is  very  great,  and  the  impreffions  of  thefe  apparent 
motions  continue  a little  time  after  he  has  experienced  them ; 
and  he  is  perftfeded  to  incline  the  contrary  way  to  counteract 
• - their 


OF  VERTIGO. 


Sect.  XX.  7. 


ns 


their  effects ; and  either  immediately  falls,  or,  applying  his  handt 
to  the  buiiding,  ufes  hismufeular  feelings  to  prefervehis  perpen- 
dicular attitude,  contrary  to  the  erroneous  perfuafions  of  his 
eyes : whilft  the  perfon  who  walks  in  the  dark  flaggers,  but 
without  dizzinefs  ; for  he  neither  has  the  fenfation  of  moving 
objects  to  take  off  his  attention  from  his  mufcuiar  feelings,  nor 
has  he  the  fpeddra  of  thofe  motions  continued  on  his  retina  to 
add  to  his  coufufion.  It  happens  indeed  fometimes  to  one  Hand- 
ing on  a tower,  that  the  idea  of  his  not  having  room  to  extend  his 
bafe,  by  moving  one  of  his  feet  outwards  when  he  begins  to  in- 
cline, fuperadds  fears  to  his  other  inconveniencies ; which,  tike 
furprife,  joy,  or  any  great  degree  of  fenfation,  enervates  him  in 
a moment,  by  employing  the  whole  fenforial  power,  and  by 
thus  breaking  all  the  affociated  trains  and  tribes  of  motion. 

7.  The  irritative  ideas  of  objerifs,  whilft  we  are  awake,  are 
perpetually  prefent  to  our  fenfe  of  fight ; as  we  view  the  furni- 
ture of  our  rooms,  or  the  ground  we  tread  upon,  throughout 
the  whole  day  without  attending  to  it.  And  as  our  bodies  arc 
never  at  perfect  reft  during  our  waking  hours,  thefe  irritative 
ideas  of  objects  are  attended  perpetually  with  irritative  ideas  of 
their  apparent  motions.  The  ideas  of  apparent  motions  are 
always  irritative  ideas,  becaufe  we  never  attend  to  them,  whe- 
ther we  attend  to  the  objedls  themfelves,  or  to  their  real  mo- 
tions, or  to  neither.  Hence  the  ideas  of  the  apparent  motions 
of  objedfs  are  a complete  circle  of  irritative  ideas,  which  conti- 
nue thoughout  the  day. 

Alfo  during  our  waking  hours,  there  is  a perpetual  confufed 
found  of  various  bodies,  as  of  the  wind  in  our  rooms,  the  ftre, 
diftant  converfations,  mechanic  buftnefs:  this  continued  buzz, 
as  we  are  feldom  quite  motionlefs,  changes  its  loudnefs  perpe- 
tually, like  the  found  of  a bell,  which  rifes  and  falls  as  long  as 
it  continues,  and  feems  to  pulfate  on  the  ear.  This  any  one 
may ' experience  by  turning  himfelf  round  near  a water-fall; 
or  by  ftriking  a glafs  bell,  and  then  moving  the  direction  of  its 
mouth  towards  the  ears,  or  from  them,  as  long  as  its  vibrations 
continue.  Hence  this  undulation  of  indiftindt  found  makes 
another  concomitant  circle  of  irritative  ideas,  which  continues 
thoughout  the  day. 

W e hear  this  undulating  found,  when  we  are  perfectly  at 
reft  curfeives,  from  other  fonorious  bodies  befides  bells  ; as 
from  two  organ-pipes,  which  are  nearly  but  not  quite  in  uni- 
fon,  when  they  are  founded  together.  When  a bell  is  ftruck, 
the  circular  form  is  changed  into  an  eliptic  one  ; the  longeft 
axis  of  which,  as  the  vibrations  continue,  moves  round  the  peri- 
pher  of  the  bell ; and  when  either  axis  of  this  elipfe  is  point- 


%*l 6 OF  VERTIGO.  ' Sect.  XX.  8,9. 

eu  towards  our  ears,  the  found  is  louder ; and  lefs  when  the 
intermediate  parts  of  the  elipfe  are  oppofiteto  us.  The  vibra- 
tions of  the  two  organ-pipes  may  be  coirfpared  to  Nonius’s 
rule ; the  found  is  louder  when  they  coincide,  and  lefs  at  the 
■intermediate  times.  But,  as  the  found  of  bells  is  the  moll  fami- 
liar of  thofe  founds,  which  have  a confiderable  battement,  the 
vertiginous  patients,  who  attend  to  the  irritative  circles  of  founds 
above  defcribed,  generally  compare  it  to  the  noife  of  bells. 

The  periftaltic  motions  of  our  fton&ach  and  inteftines,  and 
the  fecretioas  of  the  various  glands,  are  other  circles  of  irrita- 
tive motions,  fome  of  them  more  or  lefs  complete,  according 
to  our  abftinence  or  fatiety. 

So  that  the  irritative  ideas  of  the  apparent  motions  of  ob- 
jedts,  the  irritative  battements  of  founds,  and  the  movements 
of  our  bowels  and  glands  compofe  a great  circle  of  irritative 
t-ribes  of  motion:  and  witen  one  confiderable  part  of  this  circle 
of  motions  becomes  interrupted,  the  whole  proceeds  in  contu- 
sion, as  defcribed  in  Section  XVII.  1.  7.  on  Catenation  of 
Motions. 

8.  Hence,  a violent  vertigo,  from  whatever  caufe  it  hap- 
pens, is  generally  attended  with  undulating  noife  in  the  head, 
perverflons  of  the  motions  of  the  ftomach  and  duodenum,  un- 
ufual  execretion  of  bile  and  gaftic  juice,  with  much  pale  urine, 
fometimes  with  yellownefs  of  the  ikin,  and  a dilordered  lecre- 
tion  of  almoft  every  gland  of  the  body,  till  at  length  the  arte- 
rial fyftem  is  a heeled,  and  fever  fucceeds. 

Thus  bilious  vomitings  accompany  the  vertigo  occafioned 
by  the  motion  of  a {hip , and  when  the  brain  is  rendered  ver- 
tiginous by  a paralytic  affection  of  any  part  of  the  body,  a vo- 
miting generally  enfues,  and  a great  difeharge  of  bile  : and 
hence  great  iniuries  cf  the  head  from  external  violence  are  Suc- 
ceeded, with  bilious  vomiting,  and  fometimes  with  abfeefies  of 
the  liver.  And  hence,  when  a patient  is  inclined  to  vomit  iron* 
other  caufes,  as  in  fome  fevers,  any  motions  of  the  attendants  in 
his  room,  or  of  himfelf,  when  he  is  raifed  or  turned  in  his  bed, 
prefen:]  y induces  tne  vomiting,  by  fuperadding  a degree  of  vertigo. 

9.  And  converfely  it  is  very  uluai  with  thofe  whofe  fto- 
machs  are  aftedted  from  internal  caufes,  to  be  afflicted  with  ver- 
tigo, and  noife  in  the  head  ; ftich  is  the  vertigo  of  drunken  peo- 
ple, which  continues,  when  their  eyes  are  clofed,  and  them- 
felves  in  a 'recumbent  pofture,  as  well  as  when  they  are  in  an 
ereft  pofture,  and  have  their  eyes  open.  And  thus  the  irrita- 
tion of  a ftone  in  the  bile-du£t,  cr  in  the  ureter,  or  an  inflam- 
mation of  any  of  the  inteftines,  are  accompanied  with  vomit- 
ings and  vertigo. 

o b - 

In 


Sj£CT.  XX.  10. 


OF  VERTIGO. 


1 77 

In  thefe  cafes,  the  irritative  motions  of  the  ftomach,  which 
are  in  general  not  attended  to,  become  fo  changed  by  foine 
unnatural  ftimulus,  as  to  become  uneafy,  and  excite  our  fen- 
fation  or  attention.  And  thus  the  other  irritative  trains  of  mo- 
tions, which  are  affcciated  with  it,  become  disordered  by  their 
fvmpathy.  The  fame  happens  when  a piece  of  gravei  flicks 
in  the  ureter,  or  when  fome  part  of  the  inteftinal  canal  be- 
comes inflamed.  In  thefe  cafes,  the  irritative  mufcular  mo- 
tions are  firfl;  diftributed  by  unufual  ftimulus,  and  a difcrdered 
adion  of  the  fenfual  motions,  or  dizzinefs  enfues.  While  in 
fea-ficknefs  the  irritative  fenfual  motions,  as  vertigo,  precedes  3 
and  the  difordered  irritative  mufcular  motions,  as  thole  of  the 
ftomach  in  vomiting,  follow. 

10.  When  thefe  irritative  motions  are  difturbed,  if  the  de- 
gree be  not  very  great,  the  ex-ertion  of  voluntary  attention  to 
any  other  object,  or  any  fudden  fenfation,  will  disjoin  thefe  new 
habits  of  motion.  Thus  fome  drunken  people  have  become 
fober  immediately  when  any  accident  has  ftrongly  excited  their 
attention;  and  fea-ficknefs  has  vanilhed  when  the  fhip  has 
been  in  danger.  Hence,  when  our  attention  to  other  objects 
is  mold  relaxed,  as  juft  before  we  fall  afleep,  or  between  our 
reveries  when  awake,  thefe  irritative  ideas  or  motion  and  found 
are  mold  liable  to  be  perceived ; as  thofe  who  have  been  at  fea, 
or  have  travelled  long  in  a coach,  feem  to  perceive  the  vibrations 
of  the  fhip,  or  the  rattling  of  the  wheels,  at  thefe  intervals ; 
which  ceafe  again,  as  foon  as  they  exert  their  attention.  That 
is,  at  thofe  intervals  they  attend  to  the  apparent  motions,  and 
to  the  battement  of  founds  of  the  bodies  around  them,  and  for 
a moment  miftake  them  for  thofe  real  motions  of  the  fhip,  and 
noife  of  wheels,  which  they  had  lately  been  accuftomed  to; 
or  at  thefe  intervals  of  reverie,  or  on  the  approach  of  fleep, 
thefe  fuppofed  motions  or  founds  may  be  produced  intirely  by 
-imagination.  - 

We  may  conclude' from  this  account  of  vertigo,  that  fea- 
ficknefs  is  not  an  effort  of  nature  to  relieye  herfelf,  but  a ne~ 
ceffary  confequence  of  the  affociations  or  catentations  of  ani- 
mal motions  ; .and  may  thence  infer,  that  the  vomiting,  which 
attends  the  gravel  in  the  ureter,  inflammations  of  the  bowels, 
and  the  commencement  ol  fome  levers,  has  a fimilar  origin, 
and  is  net  always  an  effort  of  the  vis  medicatrix  naturae.  But 
where  the  action  of  the  organ  is  the  immediate  confequence 
of  the  ftimulating  caufe,  it  is  frequently  exerted  to  diflodge  that 
ftimulus,  as  in  vomiting  up  an  emetic  drug  ; at  other  times,  the 
adtion  of  an  organ  is  a general  effort  to  relieve  pain,  as  in  ccn- 
vulftons  of  the  locomotive  rnufcles ; other  adtiens  drink  up 

- acid 


OF  VERTIGO. 


Sect.  XX.  ir„ 


and  carry  on  the  fluids,  as  in  absorption  and  fecretion;  all 
which  may  be  termed  efforts  of  nature  to  relieve,  or  to  pre- 
ferve  herfelf. 

1 1 . The  cure  of  vertigo  will  frequently  depend  on  our  pre- 
vioufly  inveftigating  the  caufe  of  it,  which,  from  what  has 
been  delivered  above,  may  originate  from,  the  diforder  of  any 
part  of  the  great  tribes  of  irritative  motions,  and  of  the  affoci- 
ate  motions  catenated  with  them. 

Many  people,  when  they  arrive  at  fifty  or  fixty  years  of  age, 
are  affedted  with  flight  vertigo,  which  is  generally,  but  wrongiy 
afcribed  to  indigeftion,  but  in  reality  ariles  from  a beginning 
defect  of  their  fight ; as  about  this  time  they  alfo  find  it  ne- 
ceflary  to  begin  to  ule  fpedtacles,  when  thev  read  fmall  prints, 
efpecially  in  winter,  or  by  candle  light,  but  are  yet  able  to  read 
withoutthem  during  the  fummerdays,  when  the  light  is  ftronger. 
Thefe  people  do  not  fee  objedfs  fo  diftindtly  as  formerly, 
and  by  exerting  their  eyes  more  than  ufual,  they  perceive  the 
apparent  motions  of  objedts,  and  confound  them  with  the  real 
motions  of  them ; and  therefore  cannot  accurately  balance 
themfelves  fo  as  eafily  topreferve  their  perpendicularity  bv  them. 
That  is,  the  apparent  motions  of  objedts,  which  are  at  reft, 
as  we  move  by  them,  fhould  only  excite  irritative  ideas  : but 
as  thefe  are  now  become  lets  diftincl,  owing  to  the  beginning 
imperfedlion  of  our  fight,  we  are  induced,  voluntarily,  to  at- 
tend to  them  ; and  then  thefe  apparent  motions  become  fuc- 
ceeded  by  fenfation ; and  thus  the  other  parts  of  the  trains  of 
irritative  ideas,  or  irritative  mul'cular  motions,  become  difor- 
dered,  as  explained  above.  In  thele  cafes  of  flight  vertigo,  I 
have  always  promifed  my  patients,  that  they  would  get  free 
from  it  in  two  or  three  months,  as  they  fhould  acquire  the  ha- 
bit of  balancing  their  bodies  by  lefs  difiindt  objedts,  and  have 
feidom  been  miftaken  in  my  prognoftic. 

There  is  an  auditory  vertigo,  which  is  called  a noile  in  the 
head,  explained  in  No.  7.  of  this  fedtion, which  alio  is  very  liable 
to  affect  people  in  the  advance  of  life,  and  is  owing  to  their 
hearing  lefs  perfedtly  than  before.  This  is  fometimes  called  a 
ringing,  and  fometimes  a finging,  or  buzzing,  in  the  ears,  and 
is  occafioned  by  our  firft  experiencing  a dilagreeable  fenfation 
from  ournotbeing  able  diftindtly  to  hear  the  founds  we  ufed  for- 
merly to  hear  diftindtly.  And  this  dilagreeable  fenfation  excites 
defire  and  confequent  volition ; and  when  we  voluntarily  attend 
to  fmall  indiftindt  founds,  even  the  whifpering  of  the  air  in  a 
room,  and  the  pulfations  of  the  arteries  of  the  ear,  are  fucceed- 
ed  by  fenfation;  which  minute  founds  ought  only  to  have  pro- 
dutxd  irritative  fenfuai  motions,  or  unpercived  ideas.  Sec  feet 

VrMT 


Sect.  XXL  OF  DRUNKENNESS.  179 

XVII-  3-  6.  Thefe  patients  after  a while  lofe  this  auditory 
vertigo,  by  acquiring  a new  habit  of  not  attending  voluntarily  to 
thefe  indiftindl  founds,  but  contenting  themfelves  with  the  icfs 
accuracy  of  their  fenie  of  hearing. 

Another  kind  of  vertigo  begins  with  the  difordered  adfiori 
of  fome  irritative  mufcular  motions,  as  thofe  of  the  ftomach 
from  intoxication,  or  from  emetics  ; or  thofe  of  the  ureter, 
from  the  ftimulus  of  a ftone  lodged  in  it;  and  it  is  probable, 
that  the  difordered  motions  of  fome  of  the  great  congeries  of 
glands,  as  of  thofe  which  form  the  liver,  or  of  the  inteftinai  ca- 
nal, may  occafion  vertigo  in  confequence  of  their  motions  be- 
ing affociated  or  catenated  with  the  great  circles  of  irritative 
motions ; and  from  hence  it  appears  that  the  means  of  cure 
mull:  be  adapted  to  the  caufe. 

To  prevent  fea-ficknefs,  it  is  probable,  that  the  habit  of 
Twinging,  for  a week  or  two  before  going  on  Clipboard,  might 
be  of  fervice.  For  the  vertigo  from  failure  of  light,  l'pedlacles 
may  be  ufed.  For  the  auditory  vertigo,  asther  may  be  dropt 
into  the  ear  to  ftimulate  the  part,  or  to  dilTolve  ear-w'ax.  if  fuch 
be  a part  of  the  caufe.  For  the  vertigo  ariimg  from  indigef- 
tion,  the  Peruvian  bark,  and  a blifter,  are  recommended.  And 
for  that  owing  to  a ftone  in  the  ureter,  venefedlion,  cathartics, 
opiates,  fal  foda  aerated. 

12.  Definition  cf  vertigo.  1.  Some  of  the  irritative  fenfual, 
or  mufcular  motions,  which  were  ufually  not  fucceeded  by  fen- 
fa  tion,  are  in  this  difeafe  fucceeded  by  fenfation  ; and  the  trains 
or  circles  of  motions,  which  were  ufually  catenated  with  them, 
are  interrupted,  or  inverted,  or  proceed  in  confulion.  2.  The 
fenlitive  and  voluntary  motions  continue  undifturbed.  3.  The 
affociate  trains  or  circles  of  motions  continue  ; but  their  cate- 
nations with  fome  of  the  iriitative  motions  are  difordered,  or 
inverted,  or  diflevered. 

SECT.  XXL 

ON  DRUNKENNESS. 

I.  Sleep  from  fatiety  of  hunger.  From  rocking  children. 
From  uniform  founds.  2.  Intoxication  from  common  food 
after  fatigue  and  inanition.  3.  From  wine  or  opium. 
Chilnefs  after  meal's.  Vertigo.  Why  pleafure  is  produced 
by  intoxication,  and  by  fwinging  and  rocking  children. 
And  why  pain  is  relieved  by  it.  4.  Why  drunkards  f ag- 
ger andfammer , and  arc  liable  to  weep.  5.  And  become 
delirious,  fleepy , and ftupid.  6,  Or  make  pale  urine  and 
B b vomit , 


iScj  OF  DRUNKENNESS.  ' Sect. XXI.  1,2: 

vomit,  y.  Objects  are  feen  double.  8.  Attention  of  the 
mind  diminifkes  drnnlcennefs.  9.  Difordered  irritative 
motions  of  all  the  fenfes.  10.  Difeafes  from  drunkennejs 
ia.  Definition  of  drunkennejs. 

1.  In  the  Hate  of  nature,  when  the  fenfe  of  hunger  is  appealed 
by  the  ftimulus  of  agreeable  food,  the  buiinefs  of  the  day  is 
over,  and  the  human  lavage  is  at  peace  with  the  world,  he  then 
exerts  little  attention  to  external  objects,  pleafing  reveries  of 
imagination  fucceed,  and  at- length  fleep  is  the  re-iult : till  the 
nourifhment  which  he  has  procured,  is  carried  over  every  part 
of  the  fyftem  to  repair  the  injuries  of  afition,  and  he  awakens 
with  frefh  vigour,  and  feds  a renewal  of  his  fenfe  of  hunger. 

The  juices  of  fome  bitter  vegetables,  as  of  the  poppy  and  the 
laurocerafus,  and  the  ardent  fpirit  produced  in  the  fermentation  of 
the  fugar  found  in  vegetable  juices,  are  fo  agreeable  to  the  nerves 
of  the  flomach,  that,  taken  in  a fmall  quantity,  they  inflantly 
pacify  the  fenfe  of  hunger;  and  the  inattention  to  external  fli- 
muli,  with  the  reveries  of  imagination,  and  fleep,  fucceed,  in  the 
fame  manner  as  when  the  flomach  is  filled  with  other  lefs  in- 
toxicating food. 

This  inattention  to  the  irritative  motions,  cccafioned  bv  exter- 
nal ftimuli,  is  a very  important  circumflance  in  the  approach  of 
ileep,  and  is  produced  in  young,  children  by  rocking  their  cra- 
dles ; during  which  all  vifible  objedts  become  indiflincl  to  them. 
An  uniform  foft  repeated  found,  as  the  murmurs  of  a gentle 
current,  or  of  bees,  are  faid  to  produce  the  fame  effect,  by 
prefenting  indiflincl  ideas  of  inconfequential  founds,  and  by  thus 
Healing  our  attention  from  other  objects,  whilfl  by  their  con- 
tinued reiterations  they  become  familiar  themfelves,  and  we 
ceafe  gradually  to  attend  to  any  thing,  and  fleep  enfues. 

2.  After  great  fatigue  or  inanition,  when  the  flomach  is  fud- 
denly  filled  with  fieffi  and  vegetable  food,  the  inattention  to  ex- 
ternal ftimuli  and  the  reveries  of  imagination  become  fo  confpi- 
cuous  as  to  amount  to  a degree  of  intoxication.  The  fame  is 
at  any  time  produced  by  fuperadding  a little  wine  or  opium  to 
our  common  meals;  or  by  taking  thele  feparately  in  confider- 
able  quantity ; and  this  more  efficacioufly  after  fatigue  or  ina- 
nition ; becaufe  a lefs  quantity  of  any  ftimulating  material  will 
excite  an  organ  into  energetic  action,  after  it  has  lately  been 
torpid  from  defedl  of  ftimulus  ; as  objects  appear  more  lumi- 
nous after  we  have  been  in  the  dark;  and  becaufe  the  fufpen- 
fion  of  volition,  which  is  the  immediate  caufe  of  fleep,  is  l’ooner 
induced,  after  a continued  voluntary  exertion  has  in  part  e:t- 
hauiled  the  fenforial  power  of  volition;  in  the  fame  manner  as 


Sect.  XXL  3.  OF  DRUNKENNESS.  181 

we  cannot  contract  a Tingle  mufcle  long  together  without  inter- 
nals of  inaction. 

3.  In  the  beginning  of  intoxication  we  are  inclined  to  fleep, 
as  mentioned  above,  but  by  the  excitement  of  external  circum- 
ftances  as  of  noife,  light,  hufmefs,  or  by  the  exertion  of  volition, 
we  prevent  the  approaches  of  it,  and  continue  to  take  into  our 
ftomach  greater  quantities  of  the  inebriating  materials.  By  thefe 
means  the  irritative  movements  of  the  ftomach  are  excited  into 
greater  aflion  than  is  natural;  and,  in  confequence,  all  the  irri- 
tative tribes  and  trains  of  motion  which  are  catenated  with  them, 
Become  fufceptibk  of  ftronger  action  from  their  accuftomed  If  i- 
muli ; becaufe  thefe  motions  are  excited  both  by  their  ufual  ir- 
ritation, and' by  their  aflociation  <with  the  increafed  adlions  of 
the  ftomach  and  ladteals.  die  nee  the  fkin  glows,  and  the  heat 
of  the  body  is  increafed,  by  the  more  energetic  adfion  of  the 
whole  glandular  fyftem : and  pleafure  is  introduced  in  confe- 
quence of  thefe  increafed  motions  from  internal  ftimulus.  Ac- 
cording to  Law  5.  3e£t.  IV.  on  Animal  Caufation. 

From  this  great  increafe  of  irritative  motions  from  internal 
'ftimulus,  and  the  increafed  fenfation  introduced  into  the  fyftem 
;in  confequence ; and  fecondly,  from  die  increafed  fenfitive  mo- 
tions in  confequence  of  this  additional  quantity  of  fenfation,  fo 
much  fenforial  power  is  expended,  that  the  voluntary  power 
"becomes  feebly  exerted,  and  the  irritation  from  the  ftimulus  of 
external  objects  is  lefs  forcible ; the  external  parts  of  the  eye 
are  not,  therefore,  voluntarily  adapted  to  the  diftances  of  objedts ; 
whence  the  apparent  motions  of  thofe  objects  either  are  feen 
double,  or  become  too  indiftindt  for  the  purpofe  of  balancing 
the  body,  and  vertigo  is  induced. 

Hence  we  become  acquainted  with'that  very  curious  circum- 
ftance,  why  the  drunken  vertigo  is  attended  with  an  increafe  of 
pleafure ; for  the  irritative  ideas  and  motions  oecafioned  by  in- 
ternal ftimulus,  that  were  not  attended  to  in  our  fober  hours, 
are  now  juft -fo  much  increafed  as  to  be  fucceeded  by  pleafure- 
able  fenfation,  in  the  fame  manner  as  the  more  violent  motions 
of  our  organs  are  fucceeded  by  painful  fenfation.  And  hence  a 
greater  quantity  of  pleafureable  fenfation  is  introduced  into  the 
conftitution ; which  is  attended  in  fome  people  with  an  increafe 
of  benevolence  and  good  humour. 

Iftheapparentmotions  ofobjedbs  are  much  increafed,  as  when 
we  revolve  on  one*  foot,  or  are  fwung  on  a rope,  the  ideas  of 
thefe  apparent  motions  are  alfo  attended  to,  and  are  fucceeded 
with  pleafureable  fenfation,  till  they  become  familiar  to  us  by 
irequent  ufe.  Hence  children  are  at  firft  delighted  with  thefe 
".kinds  of  exercife,  and  with  riding,  and  failing  ; and  hence  rock- 

ing 


J&2 


OF  DRUNKENNESS. 


Sect.  XXI.  4, 5. 

ing  young  children  inclines  them  to  Deep.  For  though  in.  the 
vertigo  from  intoxication  the  irritative  ideas  of  the  apparent  mo- 
tions of  objects  are  indiftindt  from  their  decreafe  of  energy  ; vet, 
in  the  vertigo  occafioned  by  rocking  or  fvvinging,  the  irritative 
ideas  of  the  apparent  motions  of  objects  are  increafed  in  energv  ; 
and  hence  they  induce  pleafure  into  the  fyftem,  but  are  equaiiy 
indiftindl,  and  in  confequence  equally  unfit  to  balance  ourielvts 
by.  This  addition  of  pleafure  precludes  defire  or  averfion,  and 
in  confequence  the  voluntary  power  is  feebly  exerted  ; and  on 
this  account  rocking  young  children  inclines  them  to  fleep. 

In  what  manner  opium  and  wine  act  in  relieving  pain,  is  ano- 
ther article  that  well  defgrves  our  attention.  There  are  many 
pains  that  originate  from  defedt  as  weli  as  from  excels  of  ftimu- 
lus ; of  thefe  are  thofe  of  the  fix  appetites  of  hunger,  thirft,  luft, 
the  want  of  heat,  of  diftention,  and  of  frefii  air.  Thus,  if  our 
cutaneous  capillaries  ceafe  to  a£t  from  the  diminifhed  ftimulus 
of  heat,  when  we  are  expofed  to  cold  weather,  or  our  ftomach 
is  uneafyfor  want  of  food;  theie  are  both  pains  from  detect  cf 
stimulus,  and  in  confequence  opium,  v.-hich  ftimulates  all  the 
moving  fyftem  into  increafed  action,  muft  relieve  them.  But 
this  is  not  the  cafe  in  thofe  pains  which  arife  from  excefs  of  fti- 
mulus,  as  in  violent  inflammations;  in  thefe  the  exhibition  of 
opium  is  frequentlyinjurious,  by  increafing  theactionof  thtfvfi 
tem,  already  too  great,  as  in  inflammation  cf  the  bowels  mo;  mi- 
cation  is  often  produced  by  the  ftimulus  of  opium.  Where, 
ho\vever,  no  fuch  bad  confequences  follow,  the  ftimulus  of 
opium,  by  increafing  all  the  motions  of  the  fyftem,  expends  lo 
much  of  the  fenforial  power,  that  the  actions  of  the  whole  fyf- 
tem foon  become  feebler,  and  in  confequence  thofe  which  pro- 
duced the  pain  and  inflammation. 

4.  When  intoxication  proceeds  a little  further,  the  quantity1 

of  pleafureable  feuiation  is  fo  far  increaled,  that  all  delire 
ceafes,  for  there  is  no  pain  in  the  fyftem  to  excite  it.  Hence, 
the  voluntary  exertions  are  diminifhed,  ftaggering  and  ftam- 
mering  fucceed;  and  the  trains  ct  ideas  become  more  and  more 
inconfiftent,  from  this  defect  of  voluntary  exertion,  as  explained 
in  the  fedtions  on  fleep  and  reverie;  whilft  thofe  paflions  which 
are  unmixed  with  volition,  are  more  vividly  felt,  and  fhewn 
with  lefs  referve:  hence  pining  dove,  or  fuperftitious  fear,  and 
the  maucjling’  tear  dropped  on  the  remembrance  of  the  molt 
trifling  diftrefs.  « 

5.  At  length  all  thefe  circumftances  are  increafed  : the  quan- 
tity cf  pleafure'  introduced  into  the  fyftem  by  the  increafed  ir- 
ritative mufeuhr  motions  of  the  whole  fanguiferous,  and  glan- 
dular, a-nd  abforbent  fyftems,  becomes  fo  great,  that  the  or- 

' ....  . . garts 


Sect.  XXI.  6, 7,8,  OF  DRUNKENNESS.  183 

gans  of  fenfe  are  more  forcibly  excited  into  action  by  this  in- 
ternal pleafureable  fenfation,  than  by  the  irritation  from  the 
ftimulus  of  external  objects.  Hence  the  drunkard  ceafes  to 
attend  to  external  ftimuli ; and  as  volition  is  now  alio  fufpended, 
the  trains  of  his  ideas  become  totally  inconftftent,  as  in  dreams 
or  delirium ; and  at  length  a ftupor  fucceeds  from  the  great  ex- 
hauftion  of  fenforial  power,  which  probably  does  not  even 
admit  of  dreams,  and  in  which,  as  in  apoplexy,  nov  motions 
continue  but  thofe  from  internal  ftimuli,  from  fenfation,  and 
from  aflociation. 

6.  In  other  people  a paroxyfm  of  drunkennefs  has  another 
termination ; the  inebriate,  as  foon  as  he  begins  to  be  vertigi- 
nous, makes  pale  urine  in  -great  quantities,  and  very  fre- 
quently, and  at  length  becomes  fick,  vomits  repeatedly,  or 
purges,  or  has  profufe  fweats,  and  a temporary  fever  enfues, 
with  a quick  ftrong  pulfe.  This  in  fome  hours  is  fucceeded  by 
fleep ; but  the  unfortunate  bacchanalian  does  not  perfectly  re- 
cover himfelf  till  about  the  fame  time  of  the  fucceeding  day, 
when  hiscourfe  of inebriation  began : as  fhewn  in  Sect.  XV3I. 
1.  7.  on  Catenation.  The  temporary  fever,  with  ftrong  pulfe, 
is  owing  to  the  fame  caule  the  glow  on  the  fkin  mentioned 
in  the  third  paragraph  of  this  Section : the  flow  of  urine  and 
ficknefs  arifes  from  the  whofe  fyftem  of  irritative  motions  be- 
ing thrown  into  confufton  by  their.aflbciations  with  each  other ; 
as  in  fea-ftcknefs,  mentioned  in  Sect.  XX.  4.  on  Vertigo;  and 
which  is  more  fully  explained  in  Sect.  XXlX.  on  Diabetes. 

7.  In  this  veytigo  from  internal  caufes  we  fee  objects  double, 
as  two  candles  inftead  pf  one,  which  is  thus  explained.  Two 
lines  drawn  through  the  axes  of  our  two  eyes  meet  at  the  ob- 
ject we  attend  to : this  angle  of  the  optic  axes  increafes  or  di- 
minifhes  with  .the  lefs  or  greater  di  fiances  of  objects.  All  ob- 
jects before  or  behind  the  place  where  this  angle  is  formed, 
appear  double;  as  any  one  may  cblerve  by  holding  up  a pen 
between  his  eyes  and  the  candie  ; when  he  looks  attentively  at 
a fpot  on  the  pen,  and  carelefilv  at  the  candle,  it  will  appear 
double  ; and  the  reverfe  when  he  looks  attentively  at  the  can- 
dle, and  careleflly  at  the  pen ; fo  that  in  this  cafe  the  mufcles  of 
the  eye,  like  thofe  of  the  limbs,  ftagger  and  are  dil’obedient  to 
the  expiring  efforts  of  volition.  Numerous  objects  are  indeed 
fometimes  feen  by  the  inebriate,  occaftoned  by  the  refractions 
made  by  the  tears,  which  ftand  upon  his  eyelids. 

8.  '1  his  vertigo  alfo  continues,  when  the  inebriate  lies  in  his 
bed,  in  the  dark,  or  with  his  eyes  clofed ; and  this  more  pow- 
erfully than  when  he  is  erect,  and  in  the  light.  For  the  irri- 
tative ideas  of  the  apparent  .motions  of  cbjedts  are  new  excited 

h7 


a«4  OF  DRUNKENNESS.  Sect.  XXI.  9, ig. 

'by  irritation  from  internal  ftimulus,  or  by  afTociation  with 
other  irritative  motions ; and  the  inebriate,  like  one  in  a dream, 
believes  the  objedfs  of  thefe  irritative  motions  to  be  prefent,  and 
feels  himfelf  vertiginous.  I have  obfervea  in  this  fituation,  fo 
long  as  my  eyes  and  mind  were  intent  upon  a book,  the  fick- 
nefs  and  vertigo  ceafed,  and  were  renewed  again  the  moment 
I difcontinued  this  attention;  as  was  explained  in  the  preced- 
ing account  of  fea-ficknefs.  Some  drunken  people  have  been 
known  to  become  fober  inftantly  from  fome  accident  that  has 
ftrongly  excited  their  attention,  as  the  pain  of  a broken  bone, 
or  tire  news  of  their  houfe  being  on  fire. 

9.  Sometimes  the  vertigo  from  internal  caufes,  as  from  in- 
toxication, or  at  the  beginning  of  fome  fevers,  becomes  fo  uni- 
verfal,  that  the  irritative  motions  which  belong  to  other  organs 
of  fenfe,  are  fucceeded  by  fenfatiqn  or  attention,  as  well  as 
thofe  of  the  eye.  The  vertiginous  noife  in  the  ears  has  been 
explained  in  Sedition  XX.  on  Vertigo.  The  tafte  of  the  faliva, 
which  in  general  is  not  attended  to,  becomes  perceptible,  and 
the  patients  complain  of  a bad  tafte  in  their  mouth. 

The  common  fmells  of  the  furrounding  air  fometimes  ex- 
cite the  attention  of  thefe  patients,  and  bad  fmells  are  com- 
plained of,  which,  to  other  people,  are  imperceptible.  The 
irritative  motions  that  belong  to  the  fenfe  of  preffure,  or  of 
touch,  are  attended  to,  and  the  patient  conceives  the  bed  to 
librate,  and  is  fearful  of  falling  out  of  it.  The  irritative  mo- 
tions belonging  to  the  fenfes  of  diftention,  and  of  heat,  like 
thofe  above-mentioned,  become  attended  to  at  this  time : hence, 
we  feel  the  pulfation  of  cur  arteries  all  over  us,  and  complain 
©f  heat,  or  of  cold,  in  parts  of  the  body  where  there  is  no  ac- 
cumulation or  diminution  of  adtualheat.  All  which  are  to  be 
explained,  as  in  the  laft  paragraph,  by  the  irritative  ideas  be- 
longing to  the  various  fenfes  being  now  excited  by  internal  fti- 
muli,  or  by  their  affociations  with  other  irritative  motions. 
And  that  the  inebriate,  like  one  in  a dream,  believes  die  ex- 
ternal objedts,  which  ufually  caufed  thefe  irritative  ideas,  to 
be  now  prefent. 

xo.  The  diieafes  in  confequence  of  frequent  inebriety,  or 
of  daily  taking  much  vinous  fpirit  without  inebrietv,  coniift  in 
the  paralyfis,  which  is  liable  to  fucceed  violent  ftimulation. 
Organs,  wiiofe  actions  are  affociated  with  others,  are  fre- 
quently more  aftedted  than  the  organ  which  is  ftimulated  into 
two  violent  action.  See  Sedt.  XXI V.  2.8.  Hence,  in  drunken 
people  it  generally  happens,  that  the  fecretory  veftels  of  the 
liver  become  firft  paralytic,  and  a torpor,  with  confequent  gali- 
ftones  or  fchirrus  of  this  vifcus,  is  induced  with  concomitant 
• jaundice; 


OF  DRUNKENNESS. 


Sect. XXL  n. 


jaundice ; otherwife  it  becomes  inflamed  in  confequence  of  pre- 
vious torpor ; and  this  inflammation  is  frequently  transferred 
to  a more  fenflble  part,  which  is  aflociated  with  it,  and  pro- 
duces the  gout,  or  the  rofy  eruption  of  the  face,  or  fome  other 
leprous  eruption  on  the  head,  or  arms,  or  legs.  Sometimes  the 
ftomach.  is  flrft  affected,  and  paraiyfis  of  the  ladleal  fyflem 
is  induced ; whence  a total  abhorrence  from  flefh -food,  and. 
general  emaciation.  In  others,  the  lymphatic  fyflem  is  af- 
fected with  paraiyfis,  and  dropfy  is  the  confequence.  In  fome 
inebriates,  the  torpor  of  the  liver  produces  pain  without  ap- 
parent fchirrus,  or  gall-ftones,  or  inflammation,  or  confquent 
gout,  and  in  thefe  epilepfy  orinfanity  are  often  the  confequence. 
AH  which  wall  be  more  fully  treated  of  in  the  courfe  of  the  work. 

I am  well  aware,  that  it  is  a common  opinion,  that  the  gout 
is  as  frequently  owing  to  gluttony  in  eating,  as  to  intemperance 
in  drinking  fermented  or  fpirituous  liquors.  To  this  I anfwer, 
that  I have  feen  no  perfon  affliCled  with  the  gout,  w ho  has  not 
drank  freely  of  fermented  liquor,  as  wine  and  water,  or  lmall 
beer ; though,  as  the  difpofldon  to  all  the  difeafes  which  have 
.orginated  from  intoxication,  is  in  fome  degree  hereditary,  a 
lefs  quantity  of  fpirituous  potation  will  induce  the  gout  in  thofe 
who  inherit  the  difpofltion  from  their  parents.  To  which  1 
muft  add,  that  in  young  people  the  rheumatifm  is  frequently 
miftaken  for  the  gout. 

Spice  is  feldom  taken  in  fuch  quantity  as  to  do  any  material 
injury  to  the  fyflem ; flelh-meats,  as  wreil  as  vegetables,  are  the 
natural  diet  of  mankind;  wdth  thefe  a glutton  maybe  crammed 
up  to  the  throat,  and  fed  fat  like  a flailed  ox ; but  he  will 
not  be  difeafed,  unlefs  he  adds  fpirituous  or  fermented  liqu-or  to 
his  food.  This  is  well  known  in  the  diftilleries,  where  the 
fwine,  which  are  fattened  by  the  fpirituous  fediments  of  barrels, 
acquire  difeafed  livers.  But  mark  what  happens  to  a man, 
who  drinks  a quart  of  wine  or  of  ale,  if  he  has  not  been  habi- 
tuated to  it.  He  lol'es  the  ufe  both  of  his  limbs  and  of  his  un- 
derftanding  ! He  becomes  a temporary  idiot,  and  has  a tempo- 
rary ftroke  of  the  palfy  ! And  though  he  flowdy  recovers  after 
fome  hours,  is  it  not  reafonable  to  conclude,  that  a perpetual  re- 
petition of  fo  powerful  a poifon  muft  at  length  permanently 
affeCt  him? — If  a perfon  accidentally  becomes  intoxicated  by 
eating  a few  mufhrooms  of  a peculiar  kind,  a general  alarm 
is  excited,  and  he  is  faid  to  be  poifoned,  and  emetics  are  exhi- 
bited ; but  fo  familiariled  are  we  to  the  intoxication  from  vinous 
fpirit,  that  it  occaiions  laughter  rather  than  alarm. 

There  is,  however,  coniiderable  danger  in  too  haftily  dif- 
continuing  the  ufe  of  fo  ftrong  a ftimulus,  left  the  torpor  of  the 

fyflem. 


i86 


REPETITION  AND  Sect.  XXH.  u 

fyriem,  or  paralyfis,  fhould  fooner  be  induced  by  the  omiffior. 
than  by  the  continance  of  this  habit,  when  unfortunately  ac- 
quired. A golden  rule  for  determining  the  quantity  which, 
may  with  fafety  be  difcontinued,  is  delivered  in  Sedf.  XII.  y.  8. 

x i.  Definition  of  drunkennefs.  i . Many  of  the  irritative  mo- 
tions are  much  increafed  in  energy  by  internal  {Emulation. 

2.  A great  additional  quantity  of  pleafureable  fenfation  is 
occafioned  by  this  increafed  exertion  of  the  irritative  motions. 
And  many  fenfitive  motions  are  produced  in  confequence  of 
this  increafed  lenfation. 

3.  The  aflociated  trains  and  tribes  of  motions,  catenated 
with  the  increafed  irritative  and  fenfitive  motions,  are  difturbed, 
and  proceed  in  confufion. 

4.  The  faculty  of  volition  is  gradually  impaired ; whence 
proceed  the  inflability  of  locomotion,  inaccuracy  of  perception, 
and  ineonriftency  of  ideas;  and  is  at  length  totally  fufpended, 
and  a temporary  apoplexy  lucceeds. 


SECT.  XXII. 

OF  PROPENSITY  TO  MOTION,  REPETITION  AND 
IMITATION. 

I.  Accumulation  of  fenforial  power  in  hemiplagia , in  fleet*, 
in  cold  fit  of  fever , in  the  locomotive  mu  files,  in  the  -organs 
of  firfe.  Produces  propenfity  to  allion.  II.  Repetition 
by  three  fenforial  powers.  In  rhimes  and  alliterations,  in 
mufic , dancing , architecture , l an  df cape -pain  ting,  beauty. 
III.  I.  Perception  confifis  in  imitation.  Four  kinds  of 
imitation.  2.  Voluntary.  Dogs  taught  to  dance.  3.  Sen- 
Jitivc.  Hence  fympathy , and  all  our  virtues.  Conta- 
gious matter  of  venereal  ulcers , of  hydrophobia,  of  jail- 
fever,  of  fmall-pox,  produced  by  imitation,  and  the  fix  of 
the  embryon.  4.  Irritative  imitation.  Imitations  re - 

folvable  into  afifiociations. 

I.  1.  IN  the  hemiplagia,  when  the  limbs  on  one  fide  have 
loft  their  power  of  voluntary  motion,  the  patient  is  for  many- 
days  perpetually  employed  in  moving  thofe  of  the  other.  2. 
When  the  voluntary  power  is  fufpended  during  lleep,  there 
commences  a ceafelefs  flow  of  fenfitive  motions,  or  ideas  of 
imagination,  which  compofe  our  dreams.  3.  When,  in  the 
cold  he  of  an  intermittent  fever,  fome  parts  ot  the  lyric  m have 
for  a time  continued  torpid,  and  have  thus  expended  Ids  . than 
their  ufual  expenditure  of  fenforial  power,  a hot  fit  fucceeds, 
with  violent  action  of  thofe  veflels  which  had  previoufly  been 

quiefeent- 4 


Sect.  XXII.  2. 


IMITATION. 


187 

quiefcent.  All  thefe  are  explained  from  ail  accumulation  of 
fenforial  power  during  the  inactivity  of  fome  part  of  thefyftem. 

Befides  the  very  great  quantity  of  fenforial  power  perpetu- 
ally produced  and  expended  in  moving  the  arterial,  venous,  and 
glandular  fyftems,  with  the  various  organs  of  digeftion,  as  de- 
fcribed  in  Sedtion  XXXII.  3.  2.  there  is  alfo  a conftant  ex- 
penditure of  it  by  the  adtion  of  our  locomotive  mufcles  and  or- 
gans of  fenfe.  Thus,  the  thicknefs  of  the  optic  nerves,  where 
they  enter  the  eye,  and  the  great  expanfion  of  the  nerves  .of 
touch  beneath  the  whole  of  the  cuticle,  evince  the  greaffffan-- 
fumption  of  fenforial  power  by  thefe  fenfes.  And  our 
iual  mufcular  adfions  in  the  common  offices  of  life,  and  in  ceri- 
flantly  preferving  the  perpendicularity  of  our  bodies  during 
the  day,  evince  a confiderable  expenditure  of  the  fpirit  of  ani- 
mation by  our  locomotive  mufcles.  It  follows,  that  if  the  ex- 
ertion of  thefe  organs  of  fenfe  and  mufcles  be  for  a while  inter- 
mitted, that  fome  quantity  of  fenforial  power  muff  be  accumu- 
lated, and  a propenfity  to  activity  of  fome  kind  eniue  from  the 
increafed  excitability  of  thefyftem.  Whence  proceeds  the  irk- 
fomenefs  of  a continued  attitude,  and  of  an  indolent  life. 

However  fmall  this  hourly  accumulation  of  the  fpirit  of  ani- 
mation may  be,  it  produces  a propenfity  to  fome  kind  of  adtion ; 
but  it  neverthelefs  requires  either  delire  or  averfion,  either  plea- 
fure  or  pain,  or  fome  external  ftiinulus,  or  a previous  link  of 
affociation,  to  excite  the  fyftem  into  adtivity : thus  it  frequently 
happens,  when  the  mind  and  body  are  fo  unemployed  as  not  to 
poffefs  any  of  the  three  ftrft  kinds  of  ftimuli,  that  the  laft  takes 
place,  and  confumes  the  fmall  but  perpetual  accumulation  of 
fenforial  power.  W hence  fome  indolent  people  repeat  the  fame 
verfe  lor  hours  together,  or  hum  the  fame  tune.  Thus  the  poet  : 

Onward  he  trudged,  net  knowing  what  he  sought, 

And  whistled  as  he  went,  for  want  of  thought. 

II.  There  petitions  of  motions  may  be  at  firft  produced,  ei- 
ther by  volition,  or  by  fenfation,  or  by  irritation  ; hut  they  foon 
become  oaiier  to  perform  than  any  other  kinds  of  adtion,  be- 
caufe  they  foon  become  aftbeiated  together,  according  to  law 
the  leventh,  Sedtion  IV.  on  Animal  Caufation.  And,  becaufe 
their  rrequency  of  repetition,  if  as  much  fenforial  power  he 
produced  during  every  reiteration  as  is  expended,  adds  to  the 
lacility  of  their  produdtion. 

It  a ftimulus  be  repeated  at  uniform  intervals  of  time,  as 
defenbed  in  Sedt.  XII.  3.  3.  the  adtion,  whether  of  our  muf- 
cles or  organs  of  fenfe,  is  produced  with  ftiil  greater  facility  or 
energy  ; becaufe  the  fenforial  power  of  affociation,  mentioned 

C c above. 


REPETITION  AND  Sect.  XXII.  2. 


above,  is  combined  with  the  fenforial  power  of  irritation  ; that 
is,  in  common  language,  the  acquired  habit  aflifts  the  power  of 
the  ftimulus. 

This  not  only  obtains  in  the  annual,  lunar,  and  diurnal  ca- 
tenations of  animal  motions,  as  explained  in  Sedt.  XXXVL 
which  are  thus  performed  with  great  facility  and  energy  ; but 
in  every  lefs  circle  of  actions  or  ideas,  as  in  the  burthen  of  a 
long,  or  the  reiterations  of  a dance.  To  the  facility  and  dif- 
tindtnefs  with  which  we  hear  founds  at  repeated  intervals,  we 
owe  the  pleafure  which  we  receive  from  mulica!  time,  and  from 
poetic  time;  as  dele ribed  in  Botanic  Garden,  P.  2.  Interlude^ 
3.  And  to  this  the  pleafure  we  receive  from  the  rhitnes  and  al- 
literations of  modern  verfincation ; the  fource  of  which,  with- 
out this  key,  would  be  difficult  to  difeover.  And  to  this  like- 
wife  fhould  be  aferibed  the  beauty  of  the  duplicature  in  the  per- 
fect tenfe  of  the  Greek  verbs,  and  of  fome  Latin  ones,  as  tan^o 

• -i  • O 

tetegi,  mordeo  momordi. 

There  is  no  variety  of  notes  referable  to  the  gamut  in  the 
beating  of  the  drum ; yet  if  h be  performed  in  muflcal  time,  it  is 
agreeable  to  our  ears  ; and  therefore  this  pleafureabie  ienfation 
inuft  be  owing  to  the  repetition  of  the  divifions  of  the  founds  at 
certain  intervals  of  time,  or  mufical  bars.  Whether  thefe  times 
or  bars  are  diftinguilhed  by  a paufe,  or  by  an  emphafis  or  accent, 
certain  it  is,  that  this  diftinclion  is  perpetually  repeated  ; other- 
wife  the  ear  could  not  determine  inftantly,  whether  the  iuccef- 
fions  of  found  were  in  common  or  in  triple  time.  In  common- 
time  there  is  a divifron  between  every  two  crotchets,  or  other 
notes  of  equivalent  time,  though  the  bar  in  written  raulic  is  put 
after  every  fourth  crotchet,  or  notes  equivalent  in  time ; in  triple 
time  the  divillon  or  bar  is  after  every  three  crotchets,  or  notes 
equivalent;  fo  that  in  common  time  the  repetition  recurs  more 
frequently  than  in  triple  time.  The  grave  or  heroic  veifes  of 
the  Greek  and  Latin  poets  are  written  in  common  time;  the 
French  heroic  verfes,  and  Mr.  Anftie’s  humorous  veties  in  his 
Bath  Guide,  are  written  in  the  fame  time  as  the  Greek  and  La- 
tin verfes,  but  are  one  bar  {hotter.  The  Englilh  grave  or  he- 
roic verfes  are  mealured  by  triple  time,  as  Mr.  Pope’s  tranlla- 
tion  of  Homer. 

But  befides  thefe  little  circles  of  mufical  time,  there  are  tire 
greater  returning  periods,  and  the  ftill  more  diftant  choruffes, 
which,  like  the  rhimesat  the  ends  of  verfes,  owe  their  beauty  to 
repetition ; that  is,  to  the  facility  and  diftinclnefs  with  which  we 
perceive  founds,  which  we  expett  to  perceive,  or  have  perceiv- 
ed before;  or,  in  the  language  of  this  work,  to  the  greater  eafe 
and.  energy  with  which  our  organ  is  excited  by  the  combined 


Sect.  XXII.  3.  IMITATION.  i§9 

fenforial  powers  of  afTociation  and  irritation,  than  by  the  latter 

A certain  uniformity  or  repetition  or  parts  enters  the  very 
compofition  of  harmony.  Thus  two  odtaves  neareft  to  each 
other  in  the  fcale  commence  their  vibrations  together  after  every 
fecond  vibration  of  the  higher  one.  And  where  the  firft,  third, 
and  fifth  compofe  a chord,  the  vibrations  concur  or  coincide  fre- 
quently, though  lefs  fo  than  in  the  two  octaves.  It  is  proba- 
ble that  thefe  chords  bear  fome  analogy  to  a mixture  of  three 
alternate  colours  in  the  fun’s  fpedtrum,  feparated  by  a prifm. 

The  pleafure  we  receive  from  a melodious  fucceffion  of 
notes  referable  to  the  gamut,  is  derived  from  another  fource,  viz. 
■to  the  pendiculation  or  counreradtion  of  antagonift  fibres.  See 
Botanic  Garden,  P.  2.  Interlude^.  If  to  thefe  be  added  our 
early  afTociations  of  agreeable  ideas  with  certain  proportions  of 
.found,  I fuppofe  from  thefe  three  iources  fprings  all  the  delight 
of  mufic,  fo  celebrated  "by  ancient  authors,  and  io  enthufiaftical- 
ly  cultivated  at  prefent.  See  Sett.  XVI.  No.  10.  on  Inftindt. 

This  kind  of  pleafure,  ariling  from  repetition  ; that. is,  from 
the  facility  and  diftindtnefs  with  which  we  perceive  and  under- 
itand  repeated  fenfations,  enters  into  all  the  agreeable  arts,  and 
when  it  is, carried  to  excels,  is  termed  formality.  The  art  of 
■dancing,  like  that  of.mufic,  depends,  for  a great  part  of  the  plea- 
-fure  it  affords,  on  repetition ; architecture,  efpecially  the  Gre- 
cian, confifts  of  one  part  being  a repetition  of  another  ; and 
hence  the  beauty  of  the  pyramidal  outline  in  landfcape-painting, 
where  one  fide  of  the  picture  may  be  faid  in  fome  meafure  to 
'balance  the  other.  So  univerfally  does  repetition  contribute  to 
our  pleafure  in  the  fine  arts,  that  beauty  itlelt  has  been  denned, 
:by  fome  writers,  to  confift  in  a due  combination  of  uniformity 
and  variety.  See  Sedt.  XVI.  6, 

III.  1.  Man  is  termed,  by  Arifrotle,  an  imitative  animal : this 
propenfity  to  imitation  not  only  appears  in  the  adtions  of  chil- 
dren, but  in  all  the  cuftoms  and  faihions  of  the  world : many 
thoufands  tread  in  the  beaten  paths  of  others,  for  one  who  tra- 
verfes  regions  of  his  own  difcovery.  The  origin  of  this  pro- 
penfity to  imitation  has  not,  that  I recoiled!,  been  deduced  from 
any  known  principle:  when  any  adtion  prefents  itfelf  to  the 
view  of  a child,  as  of  whetting  a knife,  or  threading  a needle, 
the  parts  of  this  adtion,  in  refpect  of  time,  motion,  figure,  are 
imitated  by  a part  of  the  retina  of  his  eye : to  perform  this  ac- 
tion, therefore,  with  his  hands,  is  eafier  to  him  than  to  invent 
any  new  adtion,  becaule  it  confifts  in  repeating  with  another 
fet  of  fibres,  viz.  with  the  moving  mufcles,  what  he  had  juft 
performed  by  lome  parts  of  the  retina;  juft  as  in  dancing  we 

transfer 


REPETITION  AND 


*90 


Sect.  XXII. 


transfer  the  times  of  motion  from  the  actions  of  the  auditory  r 
nerves  to  the  mulcles  of  the  limbs.  Imitation,  therefore,  conliiTs  4 
of  repetition,  which  we  have  (hewn  above  to  be  the  eafieft  kind 
of  animal  action,  and  which  we  perpetually  fall  kilo  when  we 
poffefs  an  accumulation  of  fenforial  power,  which  is  not  other- 
wife  called  into  exertion. 

It  has  been  fhewn,  that  our  ideas  are  configurations  of  the 
organs  of  fenfe,  produced  originally  in  conference  of  the  fti- 
vnulus  of  external  bodies.  Anti  that  thefe  ideas,  o'r  configura-  i 
tions  of  the  organs  of  fenfe,  referable,  in  fome  property,  a cor- 
refpondent  property  ot  external  matter;  as  the  parts  of  the 
fienfes  ot  fight  and  of  touch,  which  are  excited  into  action, 
referable,  in  figure,  the  figure  of  the  Simulating  bodv ; and  pro- 
bably alfo  the  colour  and  the  quantity  of  denfity  which  they 
perceive  : as  explained  in  Sedl.  XIV.  2.  2.  Hence  it  appears, 
that  our  perceptions  themlelves  are  copies  ; that  is,  imitations  of 
fome  properties  of  external  matter ; • and  the  propenfity  to  imi- 
tation is  thus  interwoyen  with  our  exigence,  as  it  is  produced 
by  the  ftimuii  of  external  bodies,  and  is  afterwards  repeated  by 
our  volitions  and  fenfations,  and  thus  conftitutes  all  the  opera-, 
tions  of  our  minds. 

2.  Imitations  refolve  themfelves  into  four  kinds;  voluntary, j 
fenfitive,  irritative,  and  affociate.  The  voluntary  imitations! 
when  we  imitate  deliberately  the  adtions  of  others,  either 


are 


by  mimicry,  as  in  adting  a play,  or  in  delineating  a fiovve-r ; or 
in  the  common  adtions  of  our  lives,  -as  in  ourdrefs,  cockeiy, 


ianguage,  manners,  and  even  in  our  habits  of  thinking. 


Not  only  the  greateft  part  of  mankind  learn  all  the  common  ! 
arts  of  life  by  imitating  others,  but  brute  animals  feem  capable 
of  acquiring  knowledge  with  greater  facility  by  imitating  each 
other,  than  by  any  methods  by  which  we  can  teach  them;  as 
dogs  and  cats,  when  they  are  lick,  learn  of  each  other  to  eat 
grafs;  and  I fuppofe,  that  by  making  an  artificial  dog  perform 


certain  tricks,  as  in  dancing  on  his  hinder  legs,  a living  dog  might 


be  eafily  induced  to  imitate  them ; and  that,  the  readied  way  of 
inftrudfing  dumb  animals  is  by  pradtifing  them  with  others. cf 
the  fame  lpecies,  which  have  already  learned  the  arts  v.  e with 
to  teach  them.  The  important  ule  ot  imitation  in  acquiring 
natural  language  is  mentioned  in  Section  XVI.  7 and  8.  on 
Inftindh 

3.  The  fenfitive  imitations  are  the  immediate  confequences 
of  pleafure  or  pain,  and  thele  are  often  produced  even  contrary 
to  the  efforts  of  the  will.  Thus  manv  young  men,  on  feeing 
cruel  furgical  operations,  become  lick,  and  lome  even  leel  pa.  11 
in  the  parts  cf  their  own  bodies  which  they  fee  tortured  or 

wounded 


IMITATION. 


Sect.  XXII.  3. 


191 


wounded  in  others ; that  is,  they  in  fome  meafure  imitate, by  the 
exertions  of  their  own  fibres,  the  violent  actions  which  they  wit- 
neffed  in  thofe  of  others.  In  this  cafe  a double  imitation  takes 
place ; firft,  the  obferver  imitates,  with  the  extremities  of  the  optic 
nerve,  the  mangled  limbs  which  are  prefent  before  his  eyes ; then, 
by  a fecond  imitation,  he  excites  fo  violent  action  of  the  fibres 
of  his  own  limbs,  as  to  produce  pain  in  thofe  parts  of  his  own 
body  which  he  faw  wounded  in  another.  In  thefe  pains,  pro- 
duced by  imitation,  the  effedt  has  fome  fimilarity  to  the  caufe 
which  diftinguifhes  them  from  thofe  produced  by  affociation  ; 
as  the  pains  of  the  teeth,  called  tooth-edge,  which  are  produced 
by  affociation  with  difagreeable  founds,  as  explained  in  Sedt. 
XVI.  10. 

The  effedt  of  this  powerful  agent,  imitation,  in  the  moral 
world,  is  mentioned  in  Sedt.  XVI.  7.  as  it  is  the  foundation  of 
all  our  intelledtual  fympathies,  with  the  pains  and  pleafures  of 
others,  and  is,  in  confequence,  the  fource  of  all  our  virtues.  For 
in  what  confifis  our  lympathy  with  the  miferies,  or  with  the 
joys,  of  our  fellow  creatures,  but  in  an  involuntary  excitation 
of  ideas,  in  fome  meafure  fimilar  or  imitative  of  thofe  which 
we  believe  to  exift  in -the  minds  of  the  perfons  whom  w7e  cora- 
miferate  or  congratulate  ? 

There  are  certain  concurrent  or  fucceffve  adtions  of  fome 
of  the  glands,  or  other  parts  of  the  body,  which  are  pcffeffed 
of  fenfation,  which  become  intelligible  from  this  propenfity  to 
imitation.  Of  thefe  are  the  produdtion  of  matter  by  the  mem- 
branes of  the  fauces,  or  by  thefkin,  in  confequence  of  the  ve- 
nereal difeafe  previoully  affedting  the  parts  of  generation. 
Since,  as  no  fever  is  excited,  and  as  neither  the  blood  of  fuch 
patients,  nor  even  the  matter  from  ulcers  of  the  throat,  or  from 
cutaneous  ulcers,  will,  by  inoculation,  produce  the  venereal  dif- 
eafe in  others,  as  observed  by  Mr.  Hunter,  there  is  reafon  to  con- 
clude, that  no  contagious  matter  is  conveyed  thither  by  the 
blood-veffels ; but  that  a milder  matter  is  formed  by  the  adtions 
of  the  fine  veffels  in  thofe  membranes  imitating  each  other.  See 
Section  XXXIII.  2.9.  In  this  difeafe  the  actions  of  thefe  vef- 
fels  producing  ulcers  on  the  throat  and  Ikin,  are  imperfect  imi- 
tations of  thofe  producing  chanker,  or  gonorrhoea ; fince  the 
matter  produced  by  them  is  not  infectious,  while  the  imitative 
adtions  in  the  hydrophobia  appear  to  be  perfedt  relemblances, 
as  they  produce  . a material  equally  infedtious  with  the  original 
one  which  induced  them.  The  contagion  from  the  bite  of  a 
mad  dog  differs  from  other  contagious  materials,  from  its  being 
communicable  from  other  animals  to  mankind,  and  from  many 
animals  to  each  ether;  die  phenomena  attending  the  hydro- 
phobia 


ig z REPETITION,  &c.  Sect.  XXII.  3. 

phobia  are,  in  tome  degree,  explicable  on  the  foregoing  theory. 
The  infe&ious  matter  does  not  appear  to  enter  the  circulation, 
as  it  cannot  be  traced  along  the  courfe  of  the  lymphatics  frcra 
the  wound,  nor  is  there  any  fwelling  of  the  lymphatic  glands, 
nor  does  any  fever  attend,  as  occurs  in  the  fmall-pox,  and  in  ma- 
ny other  contagious  difeafes ; yet,  by  fome  unknown  procefs,  the 
difeafe  is  communicated  from  the  wound  to  the  throat,  and  that 
many  months  after  the  injury,  fo  as  to  produce  pain  and  hy- 
drophobia, with  a fecretion  of  infectious  faliva  of  the  fame  kind 
as  that  of  the  mad  dog  which  inflicted  the  wound. 

This  fuhjeCt  is  very  intricate.  It  would  appear,  that  by  cer- 
tain morbid  aCtions  of  the  falivary  glands  of  the  mad  dog,  a 
peculiar  kind  of  faliva  is  produced;  which  being  inftilled  into 
a wound  of  another  animal,  ftimulates  the  cutaneous  or  mu- 
cous glands  into  morbid  adtions,  but  which  are  ineffectual  in 
refpeCt  to  the  production  of  a iirnilar  contagious  materul ; but 
the  falivary  glands,  by  irritative  fympathy,  are  thrown  into 
fimilar  aCtion,  and  produce  an  infectious  faliva  fimilar  to  that 
inftilled  into  the  wound. 

Though  in  many  contagious  fevers  a material  iirnilar  to 
that  which  produced  the  difeafe  is  thus  generated  by  imitation, 
yet  there  are  other  infeCtious  materials  which  do  not  thus  pro- 
pagate themfelves,  but  which  feem  to  adt  like  flow  poifons. 
Of  this  kind  was  the  contagious  matter  which  produced  die  jail- 
fever  at  the  affixes  at  Oxford  about  a century  ago  ; which, 
though  fatal  to  fomany,  was  not  communicated  to  their  nurfes 
or  attendants.  In  thefe  cafes  the  imitations  of  the  fine  veiTeis, 
as  above  deferibed,  appear  to  be  imperfeCt,  and  do  not  there- 
fore produce  a matter  fimilar  to  that  which  ftimulates  them  ; 
in  this  circumftance  refembling  the  venereal  matter  in  ulcers  of 
the  throat  or  fkin,  according  to  the  curious  difeovery  of  Mr. 
Hunter  above  related,  who  found,  by  repeated  inoculations, 
that  it  would  not  infect.  Hunter  on  Venereal  Difeafe,  Part  vi. 
chap.  1. 

Another  example  of  morbid  imitation  is  in  the  production 
of  a great  quantity  of  contagious  matter;  as  in  the  inoculated 
fmall-pox,  lrom  a fmall  quantity  of  it  inferted  into  the  arm, 
and  probably  ciiffufed  in  the  blood.  Thefe  particles  of  conta- 
gious matter  ftimulate  the  extremities  of  the  tine  arteries  of  the 
kin,  and  caufe  them  to  imitate  fome  properties  of  thofe  par- 
ticles of  contagious  matter,  fo  as  to  produce  a thou  fa  nd -fold 
of  a fimilar  material.  See  Se£t.  XXX  III.  2.  6.  Other  in  fian- 
ces are  mentioned  in  the  Section  on  Generation,  which  fliew 
the  probability  that  the  extremities  of  the  feminal  glands  may 
imitate  certain  ideas  of  the  mind,  or  actions  of  die  organs  of 

fenfe, 


Sect.  XXIII.  i.  CIRCULATORY  SYSTEM.  393 

fenfe,  and  thus  occafion  the  male  or  female  fex  of  the  embryon. 
See  Sea.  XXXIX.  6. 

4.  We  come  nSw  to  thcfe  imitations  which  are  not  attended 
with  fenfation.  Of  thefe  are  all  the  irritative  ideas  already  ex- 
plained, as  when  the  retina  of  the  eye  imitates,  by  its  action  or 
configuration,  the  tree  cr  the  bench  which  I fhun  in  walking 
paft  without  attending  to  them.  Other  examples  of  thefe  irri- 
tative imitations  are  daily  obiervable  in  common  life:  thus,  one 
yawning  perfon  Ilia  11  let  a whole  company  a yawning ; and  feme 
have  acquired  winking  of  the  eyes,  or  impediments  of  fpeech, 
by  imitating  their  companions  without  being  ccnfcious  of  it. 

5.  Beiides  the  three  Ipecies  of  imitations  above  deferibed,  there 
may  be  fome  affociate  motions,  which  may  imitate  each  other 
in  the  kind  as  well  as  in  the  quantity  of  their  action ; but  it  is 
difficult  to  diflinguifh  them  from  the  affociations  of  motions 
treated  of  in  Seddion  XXXV.  Where  the  addions  of  other 
perfons  are  imitated,  there  can  be  no  doubt,  or  where  we  imi- 
tate a preconceived  idea,  by  exertion  of  our  locomotive  mufcles, 
as  in  painting  a dragon;  ail  thefe  imitations  may  aptly  be  re- 
ferred to  the  lources  above  deferibed,  of  the  propenfity  to  addivity 
and  the  facility  of  repetition : at  the  fame  time  1 do  not  affirm, 
that  all  thofe  other  apparent  fenfitive  and  irritative  imitations 
may  not  be  refolvable  into  affociations  of  a peculiar  kind,  in 
which  certain  diftant  parts  of  fimilar  irritability  or  fenfibility, 
and  which  have  habitually  added  together,  may  affect  each 
other  exaddly  with  the  fame  kinds  ct  morion ; as  many  parts- 
are  known  to  fympathife  in  the  quantity  of  their  motions : and 
that,  therefore,  they  may  be  ultimately  refolvable  into  affocia- 
tions of  addion,  as  deferibed  in  Sedd.  XXXV. 


SECT.  XXIII. 

OF  THE  CIRCULATORY  SYSTEM. 

I.  The  heart  and  arteries  have  no  antagonift  mufcles.  Veins 
abjorb  the  blood , propel  it  forwards , and  dijland  the  heart: 
contraction  of  the  heart  difends  the  arteries.  Vena  por- 
tarum.  II.  Glands  which  take  their  finds  from  the  blood . 
Wi \th  long  necks , with  fiort  necks.  III.  Abforbent  fyflem.. 
IV.  Heat  given  out  from  glandular  fecretions.  Blood 
changes  colour  in  the  lungs  and  in  the  glands  and  capilla- 
ries. V.  Blood  is  abforbed  by  veins,  as  chyle  by  laCieal 
vcffels,  otherwise  they  could  not  join  their  fir  cams.  VI. 
i wo  kinds  of  f imulus,  agreeable  and  difagrecablc.  Glan- 
dular appetency.  Glands  originally poffefjcd  fenfation. 

I.  WE  now  ftep  forwards  to  illuftrate  fome  of  the  pheno- 
mena of  difeafes,  and  to  trace  out  their  moll  efficacious  me- 
thods 


*94  CIRCULATORY  SYSTEM.  Sect.  XXIII.  2^ 

thods  of  cure  ; and  /hall  commence  this  fubjecl  with  a fliort  .. 
defcription  of  the  circulatory  fyftem. 

As  the  nerves,  whofe  extremities  form  our  various  organs  , 
offenfe  and  mufcles,  are  all  joined,  or  communicate,  by  means 
of  the  brain,  for  the  convenience  perhaps  of  the  diftribution  of  , 
a fubtile  ethereal  fluid  for  the  purpofe  of  motion  ; fo  all  thofe 
velfels  of  the  body  which  carry  the  grofter  fluids  for  the  pur- 
pofes  of  nutrition,  communicate  with  each  other  by  the  heart. 

The  heart  and  arteries  are  hollow  mufcles,  and  are  there- 
fore endued  with  power  of  contrailion  in  confequence  of  fti-  .. 
mulus,  like  all  other  mufcular  fibres ; but  as  they  have  no  an-  2 
tagonift  mufcles,  the  cavities  of  the  vefiels  which  thev  form 
would  remain  for  ever  clofed,  after  they  have  contra  tied  them-  ’ 
felves,  unlefs  fome  extraneous  power  be  applied  to  again  diflend 
them.  This  extraneous  power,  in  refpedl  to  the  heart,  is  the  - : 
current  of  blood  which  is  perpetually  abiorbed  by  the  veins  from  * 
the  various  glands  and  capillaries,  and  pufhed  into  the  heart 
bv  a power  probably  very  fimilar  to  that  which  raifes  the  fap  3 
in  vegetables  in  the  fpring,  which,  according  to  Dr.  Hale’s  ex- 
periment on  the  flump  of  a vine,  exerted  a force  equal  to  a 1 
column  of  water  above  twenty  feet  high.  This  force  of  the  * 
current  of  blood  in  the  veins  is  partly  produced  by  their  ab-  1 
forbent  power,  exerted  at  the  beginning  of  every  fine  ramiri-  j 
cation  ; which  may  be  conceived  to  be  a mouth  abforbing  J 
blood,  as  the  mouths  of  the  laileals  and  lymphatics  abforb  chyle  £ 
and  lymph : and  partly  by  their  intermitted  compreflion  by 
the  pulfations  of  their  generally  concomitant  arteries ; by  ') 
which  the  blood  is  perpetually  propelled  towards  the  heart,  as  * 
the  valves  in  many  veins,  and  the  abforbent  mouths,  in  them 
ail,  will  not  fuffer  it  to  return. 

The  blood,  thus  forcibly  injected  into  the  chambers  of  the  ^ 
heart,  diftends  this  combination  of  hollow  mufcles;  till  by  the  - 
ftimulusof  diflention  they  contrail  themfelves ; and,  pulhing  j 
forwards  the  blood  into  the  arteries,  exert  fufficient  force  to  '1 
overcome,  in  lefs  than  a fecond  of  time,  the  vis  inertia;,  and 
perhaps  fome  elafticity,  of  the  very  extenfive  ramifications  of 
die  two  great  fyftems  of  the  aortal  and  pulmonary  arteries. 
The  power  neceflary  to  do  this  in  fo  fhorta  time  mull  becon- 
ilderable,  and  has  been  variously  eftimated  by  different  phyiio- 
iogifis. 

The  mufcular  coats  of  the  arterial  fyftem  are  then  brought 
into  ailicn  by  the  ftimulus  of  diftention,  and  propel  the  blood 
ro  the  mouths,  or  through  the  convulfions  which  precede  the 
fecictory  apertures  of  the  various  glands  and  capillaries. 

In  the  vefiels  of  the  liver  there  is  no  intervention  of  the 

heart ; j 


Ssct.XXIII.2,3-  CIRCULATORY  SYSTEM.  195 

heart ; but  the  vena  portarutii,  which  does  the  office  of  an  ar- 
tery, is  diftended  by  the  blood  poured  mto  it  from  the  mifen- 
teric  veins,  and  is  by  this  diftenticn  ftimulated  to  contrurit  it- 
felf,  and  propel  the  blood  to  the  mouths  of  the  numerous  glands 
which  compofe  that  vifcus. 

II.  The  glandular  fyftem  of  vefleis  may  be  divided  iuto  thofe 
which  take  i’ome  fluid  from  the  circulation,  and  thole  which 
give  fomething  to  it,  Thofe  which  take  their  fluid  from  the 
circulation  are  the  various  glands  by  which  the  tears,  bile,  mine, 
perfpiration,  and  many  other  fecrctions,  are  produced;  thele 
glands  probably  coniift  of  a mouth  to  feiedt,  a belly,  to  cligeff, 
and  an  excretory  aperture  to  emit  their  appropriated  fluids; 
the  blood  is  conveyed  by  the  power  of  the  heart  and  arteries  to 
the  mouths  of  thefe  glands,  it  is  there  taken  up  by  the  living 
power  of  the  gland,  and  carried  forward  to  its  belly  and  excre- 
tory aperture,  where  a part  is  Separated,  and  the  remainder  ab- 
forbed  by  the  veins  for  further  purpofes. 

■ Some  of  thele  glands  are  furnifhed  with  long  convoluted 
necks  or  tubes,  as  the  feminal  ones,  which  are  curioufly  feen 
when  injected  with  quickfilver.  Others  feem  to  coniift  of 
fhorter  tubes,  as  that  great  congeries  of  glands  which  confti- 
tute  the  liver,  and  thole  of  the  kidneys.  Some  have  their  ex- 
cretory apertures  opening  into  refervoirs,  as  the  urinary  and 
gall-bladders  ; and  others  on  the  external  body,  as  thofe  w'hich 
fecrete  the  tears  and  perfpirable  matter. 

Another  great  fyftem  of  glands,  which  have  very  fhort 
necks,  are  the  capillary  vefleis ; . by  which  the  infenlible  per- 
spiration is  fee  reted  on  the  flrin;  and  the  mucus  of  various 
confidences,  which  lubricates  the  interftices  of  the  cellular 
membrane,  of  the  mufcular  fibres,  and  of  all  the  larger  cavi- 
ties of  the  body.  From  the  want  of  a long  convolution  of 
vefleis,  fome  have  doubted,  whether  thele  capillaries  fhould  be 
confldered  as  glands,  • and  have  been  led  to  conclude,  that  the 
perfpirable  matter  rather  exuded  than  w^as  fecreted.  But  the 
fluid  of  perfpiration  is  not  Ample  water,  though  that  part  or  it 
which  exhales  into  the  air  may  be  fuch ; for  there  is  another 
part  of  it  which,  in  a ftate  of  health,  is  abicibcd  again;  hut 
which,  when  the  abforbents  are  difeafed,  remains  on  the  fur- 
face  of  the  fkin,  in  the  form  of  feurf,  or  indurated  mucus. 
Another  thing  which  fhews  their  limilitude  to  other  glands,  is 
their  fenflbiiity  to  certain  affeefions  of  the  mind  ; as  is  feen  in 
the  deeper  colour  of  the  flrin,  in  the  blufh  of  lhame,  or  the 
greater  palenels  of  it  from  fear. 

III.  Another  feries  of  glandular  vefleis  is  called  the  abforb- 
ent  fyftem;  thefe  open  their  mouths  into  all  the  cavities,  and 

D d upon 


196  CIRCULATORY  SYSTEM.  Sect.  XXHT.  4. 


upon  all  thofe  furfaces  of  the  body  where  the  excretory'  aper- 


tures of  the  other  glands  pour  out  their  fluids.  The  mouilis 


cf  the  abforbent  fyftem  drink  up  a part  or  the  whole  of  thefe 
fluids,  and  carry  them  forwards  by  their  living  power  to  them' 
reipetflive  glands,  which  are  called  conglobate  gland?.  There 
theie  fluids  undergo  fome  change  before  they  pals  on  into  the 
circulation  ; but  if  they  are  very  acrid,  the  conglobate  gland 
fwells,  and  fometimes  fuppurates,  as  in  inoculation  of  the. 
ftnall-pox,  in  the  plague,  and  in  venereal  abfcrptions  ; at 
other  times  the  fluid  may  perhaps  continue  there,  till  it  under- 
goes fome  chemical  change,  that  renders  it  lels  noxious ; or,, 
what  is  more  likely,  till  it  is  regurgitated  by  the  retrograde.- 
motion  of  the  gland  in  fpontaneous  fweats  or  diarrhoeas,  as 
difagreeing  food  is  vomited  from  the  ftomach. 

IV.  As  all  the  fluids  that  pal’s  through  thefe  glands  and 
capillary  veflels  undergo  a chemical  change,  acquiring  new 
combinations,  the  matter  of  heat  is  a,  the  fame  time  given  out ; 
this  is  apparent,  lince  whatever  incrcafes  inlenfible  perfpiration, 
increafes  the  heat  cl  the  Ik  in  ; and  when  the  adtion  of  thefe 
veflels  is  much  increafed  but  for  a moment,  as  in  blulhing,  a- 
vivid  heat  on  the  Ikin  is  the  immediate  confequence.  So  when, 
great  bilious  fecretioas,  or  thofe  of  any  other  gland,  are  pro- 
duced, heat  is  generated  in  the  part  in  proportion  to  the  quantity 
of  the  fecretion. 

The  heat  produced  on  the  fkin  by  blufhing  may  be  thought, 
by  fome  too  fudden  to  be  pronounced  a chemical  efFedt,  as  the 
fermentations  or  new  combinations  taking  place  in  a fluid  is  in 
general  a flower  procefs.  Yetare  there  many  chemical  mixture^ 
in  which  heat  is  given  out  as  inflantaneoullv ; as  in  lolutions 
of  metals  in  acids,  or  in  mixtures  of  eflential  oils  and  acids,  as- 
of  oil  of  cloves  and  acid  of  nitre.  So  the  bruifed  parts  of  an 
unripe  apple  become  almoft  infhntaneoufly  fwcet ; and  if  the 
ehemico-animal  procefs  of  digeflion  be  flopped  but  for  a mo- 
ment, as  by  fear,  or  even  by  voluntary  erudlation,  a great  quan- 
tity of  air  is  generated,  by  the  fermentation  which  inftantly 
fucceeds  the  flop  of  digeflion.  By  the  experiments  of  Dr.  Hales 
it  appears,  that  an  apple  during  fermentation  gave  up  above  lix 
hundred  times  its  bulk  of  air  ; and  the  materials  in  the  ftomach. 
are  luch,  and  in  fuch  a fttuation,  as  immediately  to  run  into  fer- 
mentation. when  digeflion  is  impeded. 


As  the  blood  pafies  through  the  frnall  veflels  of  the  lungs, 


which  connedt  the  pulmonary  artery  and  vein,  it  undergoes  a 
change  of  colour,  from  a dark  to  a light  red  ; which  may  be 


termed  a chemical  chance,  as  it  is  known  to  be  effected  by  an 

O 


admixture  cf  oxygene,  or  vital  air ; which,  according  to  a dif- 


coverv 


m v”* 

. - 

| Sect.XXIII.  5, 6.  CIRCULATORY  SYSTEM.  197 

■covery  of  Dr.  Prieftley,  paffes  through  the  molft  membranes, 
which  conftitute  the  files  of  thefe  veffeis.  As  the  blood  pafles 
through  the  capillary  veffeis  and  glands,  which  conned  the 
aorta  and  its  various  branches  with  their  correfpondent  veins 
in  the  extremities  of  the  body,  it  again  lofes  the  bright  red  co- 
lour, and  undergoes  feme  new  combinations  in  the  glands  or 
-capillaries,  in  which  the-  matter  of  heat  is  given  out  from  the 
iecreted  fluids.  This  procefs,  therefore,  as  well  as  the  procefs 
of  refpiration,  has  fome  analogy  to  ccmbuftion,  as.the  vital  air 
or  oxygene  feems  to  become  united  to  fame  inflammable  bafe, 
and  the  matter  of  heat  efcapes  from  the  new  acid,  which  is  thus 
produced. 

V.  After  the  blood  has  paffed  thefe  glands  and  capillaries, 
and  parted  with  whatever  they  chofe  to  take  from  it,  the  re- 
mainder is  received  by  the  veins,  which  are  a fet  of  blood-ab- 
forbing  veffeis,  in  general  correfponding  with  the  ramifications 
of  the  arterial  fyfeem.  At  the  extremity  of  the  fine  convolu- 
tions of  the  glands  the  arterial  force  ceafes:  this,  in  refperif  to 
the  capillary  veffeis,  which  unite  the  extremities  of  the  arteries 
•with  the  commencement  of  the  veins,  is  evident  to  the  eye,  on 
viewing  the  tail  of  a tadpole,  by  means  of  a folar  or  even  by  a 
common  microfcope1;  for  globules  of  blood  are  feen  to  endea- 
vour to  pafs,  and  to  return  again  and  again,  before  they  become 
abforbed  by  the  mouths  of  the  veins ; which  returning  of  thefe 
globules  evinces,  that  the  arterial  force  behind  them  has  cealed. 
The  veins  are  furnifhed  with  valves  like  the  lymphatic  abforb- 
ents ; and  the  great  trunks  of  the  veins,  and  of  the  lariteals  and 
lymphauc,  join  together  before  the  ingrefs  of  their  fluids  into 
the  left  chamber  of  the  heart ; both  which  evince,  that  the  blood 
ki  the  veins,  and  the  lymph  and  chyle  in  the  lariteals  and  lym- 
phatics, are  carried  on  by  a fimilar  force ; otherwile  the  ftream, 
which  was  propelled  with  a lefs  power,  could  not  enter  the  vef- 
feis which  concained  the  ftream  propelled  with  3 greater  power. 
From  whence  it  appears,  that  the  veins  are  a fyftem  of  veffeis 
■abforbing  blood,  as  the  laefteals  and  lymphatics  are  a fyftem  of 
•veffeis  abforbing  chyle  and  lymph.  See  Serif.  XXVII.  i„ 

VI.  The  movements  of  their  adapted  fluids  in  the  various 
veffeis  of  the  body  are  carried  forwards,  by  the  actions  of  thofe 
veffeis,  in  coufequence  of  two  kinds  of  ftimulus ; one  of  which 
may  be  compared  to  a pleafureable  fenfation,  or  defire,  inducing 
the  veffei  to  feize,  and,  as  it  were,  to  fwallovv  the  particles  thus 
delected  from  the  blood ; as  is  done  by  the  mouths  of  the  various 
glands,  veins,  and  other  abforbents,  which  may  be  called  glan- 
dular appetency.  The  other  kind  of  ftimulus  may  be  compared 
to  diiagreeable  ienfation,  or  averfion,  as  when  the  heart  has  re- 
ceived 


OF  THE  SALIVA 


198 


SrcT.  XXIV.  1. 


eeived  the  blood,  and  is  ftimulated  by  it  to  pufh  it  forwards  into 
tire  arteries:  the  fame  again  ftimulafes  the  arteries  to  contract, 
and  carry  forwards  the  blood  to  their  extremities,  the  glands  and  ; 
capillaries.  Thus  the  mefeuteric  veins  abforb  the  blood  irons*' 
the  inteftines  by  glandular  appetency,  and  carrv  it  forward  to  ' 
the  vena  ponarum;  which,  acting  as  an  artery,  contracts  idelf 
by  difagreeable  ftimuius,  and  pufh.es  it  to  its  ramified  extremi- 
ties, the  various  glands  which  conftitute  the  liver. 

It  feems  probable,  that  at  the  beginning  of  the  formation  of 3 
thefe  veflels  in  the  embiyon,  an  agreeable  fenfation  was  in 
reality  felt  by  the  glands  during  fecretion,  as  is  now  feir  in  thcSj 
add  of  fwallovving  palatable  food:  and  that  a dilagreeable  fen-  ' 
fation  was  originally  felt  bv  the  heart  from  the  diftenticn  occa- 
fioned  by  the  blood,  or  by  its  chemical  ftimuius ; but  that  by 
habit  thefe  are  all  become  irritative  motions  ; that  is,  fucli  mo-, 
tions  as  do  not  affeft  the  whole  fyltem,  except  when  the  vefiels  ■ 
are  dileaied  by  inflammation. 


SECT.  XXIV. 

OF  THE  SECRETIONS  OF  SALIVA,  AND  OF  TEARS,  I 
AND  OF  THE  LACRIMAL  SACK. 

I.  Secretion  of  faliva  increafed  by  mercury  in  the  blood . 1.  1 
By  the  food  in  the  mouth.  Drynefs  of  ihe  mouth  not  froth  1 
a deficiency  of  faliva.  2.  By  JenJitive  ideas.  3.  By  voli- 
tion. 4.  By  dijlafiteful  ( ubjlances . It  is  leereted  in  a di- 
lute and  falinc  flate.  It  then  becomes  more  vificid.  5.  Bi 
ideas  of  dijlajleful  fubflances.  6.  By  naufea.  7.  By  aver-  . 
fiion.  8.  By  catenation  with  Jlimulating  fubfances  in  the 
ear.  II.  1.  Secretion  of  tears  lefs  in  jieep.  From  /limn  l a-  , 
iion  of  their  excretory  dull.  2.  Lacrymal  fack  is  a gland,  h 
3.  Its  ufes.  4.  Fears  are  ferreted , when  the  na/al  dull  is  1 
flimulated.  5.  Or  when  it  is  excited  by  fenfation.  6.  Or 
by  volition.  7.  The  lacrymal  fack  can  regurgitate  its  con-  . 
tents  into  the  eye.  8.  Adore  tears  are  fccreted  by  a /foe  Inti  on 
with  the  irritation  of  the  na  fal  dull  of  ihe  lacrymal  /nek,  1 
than  thepunfla  lacrymalia  can  imbibe.  Of  the  gout  ir,« 
liver  and fiomach. 


T.  THE  falival  glands  drink  up  a certain  fluid  from  the  cir- 
cumfluent blood.  and  pour  it  into  the  mouth.  They  are  ioir.e- 
Cimes  ftimulated  into  action  by  the  blood  that  furrounds  their 
origin,  or  by  feme  part  of  that  heterogeneous  fluid:  tor  when 
mercurial  falts.  or  oxydes,  are  mixed  with  the  blocd,  they  Its- 
} - mulatc 


AND  TEARS. 


Sect.  XXIV.  i. 


m 


mulate  thefe  glands  into  unnatural  exertions  ; and  then  an  un- 
fual  quantity  of  faliva  is  feparated. 

As  the  faliva  fecreted  bv  thefe  glands  is  moft  wanted  during 
the  maftication  of  our  food,  it  happens,  when  the  terminations 
or  their  ducts  in  the  mouth  are  flimulated  into  action,  the  fali- 
val  glands  themfelves  are  brought  into  increafed  action  at  the 
fame  time  by  affccution,  and  feparate  a greater  quantity  of  their 
juices  from  the  blood  ; in  the  fame  manner  as  tears  are  produc- 
ed in  greater  abundance  • uring  the  famulus  of  the  vapour  of 
onions,  or  of  anv  other  acrid  material  in  the  eve. 

The  faliva  is  thus  naturally  poured  into  the  mouth  only  dur- 
ing the  Stimulus  of  our  food  in  maltication ; for  when  there 
is  too  great  an  exhalation  of  the  mucilaginous  fecretion  from 
the  membranes  which  line  the  mouth,  or  too  great  an  abforp- 
tion  of  it,  the  mouth  becomes  dry,  though  there  is  no  deficiency 
in  the  quantity  of  faliva  ; as  in  thole  who  fleep  wuh  their 
mouths  open,  and  in  tome  fevers. 

2.  Though  during  the  maftication  of  our  natural  food  the  fa- 
lival glands  are  excited  into  action  bv  the  flimulus  on  their  ex- 
cretory ducts,  and  a due  quantity  of  faliva  is  feparated  from  the 
blood,  and  poured  into  the  mouth  ; yet  2s  this  maftication  cf 
our  food  is  always  attended  with  a degree  of  pleafure,  and  that 
pleafureabie  fenfation  is  alio  connected  with  our  ideas  of  certain 
kinds  of  aliment,  it  follows,  that  when  thofe  ideas  are  reproduc- 
ed, the  pleafureabie  fenfation  arifes  along  with  them,  and  the 
falival  glands  are  excited  into  action,  and  fill  the  mouth  with 
faliva  from  this  fenlitive  afibeiation,  as  is  frequently  fbenin  dogs, 
who  Haver  at  the  fight  of  food. 

3.  We  haye  alfo  a voluntary  power  over  the  action  of  thefe 
falival  glands,  for  we  can  at  any  time  produce  a flow  of  faliva 
into  our  mouth,  and  fpitout,  or  fwallow  it  at  will. 

4.  If  any  very  acrid  material  be  held  in  the  mouth,  as  the 
root  of  pyrethrum,  or  the  leaves  of  tobacco,  the  falival  glands 
are  flimulated  into  ftronger  action  than  is  natural,  and  thence 
fecrete  a much  larger  quantity  of  faliva ; which  is  at  the  fame 
time  more  vifeid  than  its  natural  ft  Ue ; becaufe  the  lymphatics, 
that  open  their  mouths  into  the  dudts  of  the  falival  glands,  and 
on  the  membranes  which  line  the  mouth,  are  likewife  flimu- 
lated into  ftronger  adtion,  and  abforb  the  more  liquid  parts  of 
the  faliva  with  greater  avidity  : and  the  remainder  is  left  both  in 
greater  quantity  and  more  vifeid. 

The  increafed  abforption  in  the  month  bv  fome  ftimulating 
fubftances,  which  are  called  aftringents,  as  crab  juice,  is  evi- 
dent from  the  inftant  drynefs  produced  in  the  mouth  by  a fmall 
auantity  of  them,  , 

As 


■2CO 


OF  THE  SALIVA 


Sect.  XXIV.  2. 


As  the  extremities  of  the  glands  are  of  exquifite  tenuity,  as 
appears  by  their  difficulty  of  injection,  it  was  neceffarv  for  mem 
to  fecrete  their  fluids  in  a very  dilute  ftate ; and,  probablv  for 
the  purpofe  ot  ftimulating  them  into  afition,  a quantity  of  neu- 
tral fait  is  likewife  fecreted  or  formed  by  the  gland.  This  aque- 
ous and  faline  part  of  all  fecreted  fluids  is  again  reabforbed  in- 
to the  habit.  More  than  half  of  fome  fecreted  fluids  is  thus  im- 
bibed from  the  refervoirs,  into  which  they  are  poured  , as  in 
the  urinary  bladder  much  more  than  half  of  what  is  fecreted  by 
the  kidneys  becomes  reabforbed  by  the  lymphatics,  which  are 
thickly  difperfed  around  the  neck  of  the  bladder.  This  feenrs 
to  be  the  purpofe  of  the  urinary  bladders  of  flih,  as  other.wii’e 
iuch  a receptacle  for  die  urine  eculd  have  been  of  nc  ufe  to  an 
animal  immerfed  in  water. 

5.  The  idea  of  fubftanqes  difagreeably  acrid  will  alfo  produce 
a quantity  of  faliva  in  the  mouth;  as  when  we  fmell  very  pu- 
trid vapours,  we  are  induced  to  {pit  out  o.ur  faliva,  as  if  lome- 
thing  difagreeable  was  a&uallv  upon  our  palates. 

6.  When  difagreeable  food  in  the  ftomach  produces  naufea, 
a flow  of  faliva  is  excited  in  the  mouth  by  aiTociation  ; as  ef- 
forts to  vomit  arefreoueedy  produced  by  difagreeable  drugs  it} 
the  mouth  by  the  fame  kind  of  aflociation. 

7.  A preternatural  flow  of  faliva  is  likewife  fometimes  occa- 
Toned  by  a difeafe  of  the  voluntary  power  ; for  if  we  think  a- 
bout  our  faliva,  and  determine  not  to  fwallow  it,  or  not  to  l'pit 
it  out,  an  exertion  is  produced  by  the  will,  and  more  faliva  is 
fecreted  again  A our  wifh ; that  is,  by  our  averflon,  which  bears 
the  fame  analogy  to  defire  as  pain  does  to  pleafure;  as  thev 
are  only  modifications  of  the  fame  difpofition  of  the  lenlorium. 
See  Clafs  IV.  3.  2.  1. 

8.  The  quantity  of  faliva  may  alfo  be  increafed  beyond  what 
is  natural,  by  the  catenation  of  the  motions  of  thefe  glands  with 
other  motions,  or  fenlations,  as  by  an  extraneous  body  in  the 
ear,  of  which  I have  known  an  inflance  ; or  by  the  applica- 
tion of  ftizolobium.  filiqua  hirluta,  cowhage,  to  the  feat  of  die 
parotis,  as  lome  writers  have  affirmed. 

II.  1.  'File  lacrymal  gland  drinks  up  a certain  fluid  from 
the  circumfluent  blood,  and  pours  it  on  the  ball  ot  the  eye,  on 
the  upper  part  of  the  external  corner  of  the  eyelids.  Though 
it  may  perhaps  be  ftivnulated  into  the  performance  of  its  natu- 
ral aebion  by  the  blood,  which  furrounds  its  origin,  or  by  fome 
part  ot  that  heterogeneous  fluid  ; yet  as  the  tears  fecreted  In 
this  gland  are  more  wanted  at  fome  times  than  at  others,  its 
fecretion  is  variable,  like  that  cf  the  faliva  above  mentioned,  and 
is  chiefly  produced  when  its  excretory  duel  is  ftimulated  ; for 


<5 


AND  TEARS. 


20  2 


Sect.  XXI V.  2. 

in  our  common  fleep  there  feems  to  be  little  or  no  fecretion  of 
tears  ; though  they  are  occalionally  produced  by  our  fenfations- 
in  dreams. 

Thus,  when  any  extraneous  material  on  the  eye-ball,  or  the 
dry  net's  of  the  external  covering  of  it,  or  the  coldnefs  of  the 
air,  or  the  acrimony  of  tome  vapours,  as  of  onions,  {Emulates 
the  excretory  du£t  of  the  lacrymal  gland,  it  difcharges  its  con- 
tents upon  the  ball ; a quickerfecretion  takes  place  in  the  gland, 
and  abundant  tears  fuccecd,  to  moiften,  clean,  and  lubricate 
the  eye.  Theie,  by  frequent  nictitation,  are  diffufed  over  the 
whole  ball ; and  as  the  external  angle  of  the  eye  in  winking  is 
doled  fooner  than  the  internal  angle,  the  tears  are  gradually 
driven  forwards,  and  downwards  from  the  lacrymal  gland  to 
the  punCta  lacrymalia.. 

2.  The  lacrymal  fack,  with  its  pnncta  lacrymalia,  and  its 
nafalduCt,  is  a complete  gland  ; and  is  Angular  in  this  refpeCl, 
that  it  neither  derives  its  fluid  from,  nor  difgorges  it  into  the 
circulation.  The  limplicity  of  the  ftruClure  of  this  gland,  and 
both  the  extremities  of  it  being  on  the  furiace  of  the  body-, 
makes  it  well  worthy  our  minuter  obfervation ; as  the  adions 
of  more  intricate  and  concealed  glands  may  be  better  under- 
flood from  their  analogy  to  this. 

3.  This  Ample  gland  confifts  of  two  abforbing  mouths,  a 
belly,  and  an  excretory  duct.  As  the  tears  are  brought  to  the 
internal  angle  of  the  eye,  thefe  two  mouths  drink  them  up,  be- 
ing {Emulated  into  a£Eon  by  this  fluid,  which  they  ab fiord.. 
The  belly  of  tire  gland,  or  lacrymal  fack,  is  thus  filled,  in. 
which  the  faline  part  of  the  tears  is  abforbed;  and  when  the 
other  end  of  the  gland,  or  nafal  du£t,  is  {Emulated  by  the  dry- 
nefs,  or  pained  by  the  coldnefs  of  the  air,  or  afFedted  by  any 
acrimonious  duft  or  vapour  in  the  noflrils,  it  is  excited  into 
afttion,  together  with  the  fack,  and  the  tears  are  difgorged  upon, 
the  membrane  which  lines  the  noflrils,  where  they  ferve  a fecond. 
purpofe  to  moiften,  clean,  and  lubricate  the  organ  of  fmell. 

4.  When  the  nafal  du£l  of  this  gland  is  (Emulated  by  any 
very  acrid  material,  as  the  powder  of  tobacco,  ©r  volatile  fpirits,. 
it  not  only  difgorges  the  contents  of  its  belly  or  receptacle  (the 
lacrymal  fack,)  and  abforbs  haftilv  all  the  fluid  that  is  ready  for 
it  in  the  cornea  of  the  eye ; but,  by  the  affociation  of  its  motions- 
with  thofe  of  the  lacrymal  gland,  it  excites  that  alfo  into  in- 
crealed  action,  and  a large  flow  of  tears  is  poured  into  the  eve. 

5.  This  nafal  du£l  is  likewife  excited  into  ftrong  adlicn  by 
fenfidve  ideas,  as  in  grief  or  joy ; and  then  alio  by  its  afTbcia- 
tions  with  the  lacrymal  gland,  it  produces  a great  flow  of  tears, 
without  any  external  ftimulus  > as  is  more  fully  explained  in 
Se£E  XVI.  8.  on  Inftindt. 


ft.  There 


2C2 


OF  THE  SALIVA 


Sect.  XaIV.  2. 


6.  There  are  fome,  famous  in  the.  arts  of  exciting  compaf- 
fion,  who  are  faid  to  have  acquired  a voluntary  power  ct  pro- 
ducing a flow  ot  tears  in  the.  eye ; which,  from  what  has  been 
faid  in  the  fedtion  on  Inftindt  above-mentioned,  I ihould  fuf- 
peA,  is  performed  by  acquiring  a voluntary  power  over  the 
adtion  of  this  nafal  dude. 

7.  There  is  another  circumftance  well  worthy  cur  attention, 
that  when  by  any  accident  this  nafal  duct  is  obftructed,  me  lu- 
crymal  fack,  which  is  the  belly  or  receptacle  of  this  gland,  by 
flight  preffure  of  the  finger  is  enabled  to  dif  orge  its  cements 
again  into  the  eye  : perhaps  the  bile  in  the  fame  manner,  when 
tiie  biliary  ducts  are  obilt  udted,  is  returned  into  the  blood  by 
the  veflels  which  fecrete  it. 

8.  A very  important  though  minute  occurrence  muff  here 
be  ohferved,  that  though  the  lacrymal  gland  is  only  excited  into 
action,  when  we  weep  at  a diftreisrul  tale,  by  its  aifociation 
with  this  nafal  du£t,  as  is  more  fully  explained  in  Sect  XVI. 
8.  yet  the  quantity  of  tears  fecreted  at  once  is  more  than  the 
puncta  lacrymalru  can  readily  abiorb  ; which  ihews  that  the 
motions  occajioned  by  affociations  are  frequently  more  ener- 
getic than  the  original  motions  by  which  they  were  ecca- 
Jioncd : which  wc  Inal l have  occafion  to  mention  hereafter, 

to  illuftrate  why  pains  frequently  exift  in  a partdiflant  from  the 
caufe  of  them,  as  in  die  other  end  of  the  urethra,  when  a ft<  no 
flimulates  the  neck  of  tiie  bladder  ; and  why  inflammations  fre- 
quently arlfe  in  parts  diftant  from  their  caufe,  as  the  gutta  rofca 
ot  drinking  people,  from  an  inflamed  liver. 

The  inflammation  of  apart  is  generally  preceded  by  a torpor 
or  quiefcence  ot  it ; it  this  exifts  in  any  large  congeries  of  glands, 
as  in  the  liver,  or  any  membranous  part,  as  the  ftomach,  pain 
is  produced,  and  chiilineis  in  conlequence  of  the  torpor  of  rlie 
veliels.  In  this  fituation  fometimes  an  inflammation  of  the  parts 
fucceeds  the  torpor;  at  other  times  a diftant,  mere  ier.lible  part 
becomes  inflamed;  whofe  adlions  have  previ  ufv  been  afl’oei- 
ated  with  it,  and  the  torpor  of  the  tirft  part  cedes.  Tnis  1 ap- 
prehend happens,  when  the  gout  of  the  foot  lucceeds  a pain  of 
the  "biliary  duff,  or  of  the  ftomacn.  Laft'v,  it  iometimes  imp- 
pens,  that  die  pain  or  torpor  exifts  without  any  coi.tequent  in- 
flammation of  the  afFe&ed  part,  or  of  any  diftant  part  aflfociated 
with  it,  as  in  the  membranes  about  the  temple  ai.d  eve-brows 
in  hemicrania,  and  in  thefe  pains  which  cccafton  ccnwulions: 
if  this  happens  to  gouty  people,  when  it  aftedis  tiie  li\  er.  I lup-. 
pole  epileptic  fits  are  produced;  and,,  v.  hen  it  a file  is  the  iio- 
mach,  death  is  the  confequence.  In  thefe  cafes  the  pulfe  ;s 
weak,  and  the  extremities  cold,  and  iuch  medicines  as  ftinrulatc 


Sect.  XXV.  i.  OF  THE  STOMACH,  See.  203 

the  quiefeent  parts  into  action,  or  which  induce  inflammation  in 
them,  or  in  any  diftant  part  which  is  affociated  with  them,  cures 
the  prefent  pain  of  torpor,  and  faves  the  patient. 

I have  twice  feen  a gouty  inflammation  of  the  liver  attended 
with  jaundice ; the  patients,  after  a few  days,  were  both  of  them 
aftedled  with  cold  fits,  like  ague-fits,  and  their  feet  became  af- 
fedted  with  gout,  and  the  inflammation  of  their  livers  ceafed.  It 
is  probable,  that  the  uneafy  fenfations  about  the  ftomach,  and 
indigeftion,  which  precede  gouty  paroxyfms,  are  generally  ow- 
ing to  torpor,  or  flight  inflammation  of  the  liver  and  biliary  dudfs ; 
but  where  great  pain,  with  continued  ficknefs,  with  feeble  pulie, 
and  fenfation  of  cold,  aftedl:  the  ftomach  in  patients  debilitated 
by  the  gout,  that  it  is  a torpor  of  the  ftomach  itfelf,  and  deft'roys 
the  patient  from  the  great  connection  of  that  vifeus  with  the  vi- 
tal organs.  See  Sect.  XXV.  17. 

SECT.  XXV. 

OF  THE  STOMACH  AND  INTESTINES. 

£.  Of  fwalloiving  our  food.  Ruminating  animals.  2. 
Aflion  of  the  ftomach.  3.  Aflion  of  the  intefines.  Ir- 
ritative motions  connected  with  thefe , 4.  Ejfells  of  re- 

pletion. 5.  Stronger  action  of  the  fomach  and  intef  ines 
from  more  fimulatingfood.  6.  Their  aflion  inverted  by 
fill  greater  fimuli.  Or  by  difgufful  ideas.  Or  by  vo- 
lition. 7.  Other  glands  frengthe.n  or  invert  their  mo- 
tions by  fympathy.  8.  Vomiting  performed  by  intervals. 
9.  Inverfon  of  the  cutaneous  abforbents.  10.  Increafed 
fecretion  of  bile  and  pancreatic  juice.  11.  Inverfon  of 
the  la  ft  eats.  12.  And  of  the  bile-dufls.  13.  Cafe  of  a cho- 
lera. 14.  Further  account  of  the  inverfon  of  lafteals. 
15.  Iliac  pajfon.  Valve  of  the  colon.  16.  Cure  of  the 
iliac  paffton.  17.  Pain  of  gall-fone  difinguificd  from 
pain  of  the  fomach.  Gout  of  the  fomach  from  torpor ; 
from  inflammation.  Intermitting pulfe  owing  to  indigeflion. 
To  over  dofe  of foxglove.  Weak  pulfe  from  emetics.  Death 
from  a blow  on  the  fomach.  From  gout  of  the  fomach. 

1.  THE  throat,  ftomach  and  inteftines,  maybe  confidered 
as  one  great  gland  ; which,  like  the  lacrymal  fack  above- 
mentioned,  neither  begins  norends  in  the  circulation.  Though 
the  add  of  mafticating  our  aliment  belongs  to  the  fenfitive  clafs 
of  motions,  for  the  pleafure  of  its  tafte  induces  the  mufcles  of 
the  jaw  into  action  ; yet  the  deglutition  oi  it,  when  mafticated, 
is  generally,  if  not  always,  an  irritative  motion,  occafioned  by 

E e the 


204' 


OF  THE  STOMTACH’  Sect.  XXV.  2, 5,4. 

the  application  of  the  food  already  mafticated  to  the  origin  of 
the  pharix  ; in  die  fame  manner  as  we  often  fwallow  our  fpit- 
tk  without  attending  to- it. 

The  ruminating  clafs  of  animals  have-  the  power  to  invert' 
the  motion  of  their  gullet,  and  of  their  firft  ftomach,  from  the 
ftimulus  of  mis  aliment,  when  it  is  a iitde  further  prepared ; 
as  is  their  daily  practice  in  chewing  the  cud  ; and  appears  to 
the  eye  of  any  one  who  attends  to  them,  whilft  they  are  em- 
ployAl  in  this  fecond  rr.aftication  of  their  food. 

2.  When  our  natural  aliment  arrives  into  the  ftomach,  this 
organ  is  ftimulated  into  its  proper  vermicular  adtion ; which, 
beginning  at  the  upper  orifice  of  it,  and-  terminating  at  the 
lower  one,  gradually  rhixes  together  and  pulhes  forwards  the 
digefting  materials  into  the  inteftine  beneath  it. 

At  the  fame  time  the  glands,  that  fupply  the  gaftric  juices, 
which  are 'neceflary  to  promote  the  chemical  part  of  the  pro- 
cefs  of  digeftion,  are  ftimulated  to  difcharge  their  contained 
fluids,  and  to  feparate  a further  lupply  from  the  blood-vefiels  ; 
and  the  lafteals  or  lymphatics,  which  open  their  mouths  into- 
the  ftomach,  are  ftimulated  into  adlion,  and  take  up  fome  part 
of  the  digefting  materials. 

3.  The  remainder  of  thefe  digefting  materials  is  carried  for- 
wards into  the  upper  inteftines,  and  ftimulates  them  into  their 
periftaltic  motion,  fimilar  to  that  of  the  ftomach  ; which  con- 
tinues gradually  to  mix  the  changing  materials,  and  pafs  them 
along  through  the  valve  of  the  colon  to  the  excretory  end  of 
this  great  gland,  the  fphineter  ani. 

The  digefting  materials  produce  a flow'  of  bile,  and  of  pan- 
creatic juice,  as  they  pafs  along  the  duodenum,  by  ftimulating 
the  excretory  duffs  of  the  liver  and  pancreas,  which  terminate 
in  that  inteftine  ; and  other  branches  of  the  abforbent  or  lym- 
phatic fyftem,  called  lafteals,  are  excited  to  drink  up,  as  it' 
pafles,  thofe  parts  of  the  digefting  materials,  that  are  proper 
for  their  purpofe,  by  its  ftimulus  on  their  mouths. 

4.  When  the  ftomach  and  inteftines  are  thus  filled  with 
their  proper  food,  not  only  the  motions  cf  the  gaftric  glands, 
the  pancreas,  liver,  and  lafteal  velTels,  are  excited  into  action ; 
but  at  the  fame  time  the  whole  tribe  of  irritative  motions  are 
exerted  with  greater  energy-;  a greater  degree  of  warmth,  co- 
lour, plumpnefs,  and  moifturc,  is  given  to  the  fkin  from  the. 
increased  aftion  of  thofe  glands  called  capillary  veffels  ; plea- 
fureable  fenfation  is  excited,  the  voluntary  motions  are  left 
eallly  exerted,  and  at  length  fufpended  ; and  fleep  fucceeds,  un- 
lefs  it  be  prevented  by  the  ftimulus  of  furrounding  objefts,  or  by' 
voluntary  exertion,  or  by  an  acquired  habit,  which  was  original-- 


Sect. XXV.  5/6,  AND  INTESTINES.  205 

iy  produced  by  one  or  other  of  thefe  circum  (lances,  as  is  ex- 
plained in  Sect.  XXL  on  Drunkennefs. 

At  this  time  alfo,  as  the  blocd-veffels  become  replete  with 
chyle,  more  urine  is  Separated  :into  the  bladder,  and  lefs  of  it 
.•is  reabforbed  ; more  mucus  poured  into  the  cellular  membranes, 
and  lefs  of  it  reabforbed  ; the  pulfe  becomes  fuller  and  fofter, 
and  in  general  quicker.  The  reafon  why  lefs  urine  and  cel- 
lular mucus  is  abforbed  after  a full  meal,  with  fufficient  drink,  is 
owing  to  the  blood-veffels  being  fuller  ; hence  one  means  to 
promote  abforption  is  to  deereafe  the  reftftance,  by  emptying 
the  veffels  by  venefedtion.  From  this  decreafed  abforption 
the  urine  becomes  pale  as  well  as  copious,  and  the  {kin  ap- 
pears plump  as  well  as  florid. 

By  daily  repetition  of  thefe  movements,  they  ail  become 
connected  together,  and  make  a diurnal  circle  of  irritative  ac- 
tion ; and  if  one  of  this  chain  be  difturbed,  the  whole  is  liable 
to  be  put  into  diforder.  .-See  Seel.  XX.  on  Vertigo. 

5.  When  the  ftomach  and  inteftipes  receive  a quantity  of 
food,  whofe  ftimulus  is  greater  -than  ufual,  all  their  motions, 
and  thofe  of  the  glands  and  lymphatics,  are  ftimulated  into 
ftronger  action  than  ufual,  and  perform  their  offices  with  greater 
vigour,  and  in  lefs  timer  fuen  are  the  effedfs  of  certain  quan- 
tities of  fpice  or  cf  vinous  fpirit. 

6.  But  if  the  quantity  or  duration  of  thefe  ftirouli  are  fbill  Fun- 
ther  increafed,  the  ftomach  and  throat  are  ftimulated  into  a mo- 
tion, whofe  direction  is  contrary  to  the  natural  one  above  de- 
scribed; and  they  regurgitate  the  materials,  which  they  contain, 
inftead  of  carrying  them  forwards.  This  retrograde  motion 
of  the  ftomach  may  be  compared  to  the  fbetchings  of  wearied 
limbs  the  contrary  way,  and  is  well  elucidated  by  the  follow- 
fog  experiment.  Look  earneftly  for  a minute  or  two  on  an 
area,  an  inch  fquare,  of  pink  filk,  placed  in  a ftrong  light;  the 
eye  becomes  fatigued,  the  colour  hecomes  faint,  and  at  length 
vaniilies ; for  the  fatigued  .eye  can  no  longer  be  ftimulated  into 
•diredi  motions  ; then,  on  clofmg  the  eye,  a green  Ipedtrum  will 
appear  in  it,  which  is  a colour  diredfly  contrary  to  pink,  and 
which  will  appear  and  difappear  repeatedly,  like  the  efforts  in 
vomiting.  See  JSedfion  XXIX.  1 1 . 

Hence  all  thofe  drags,  which,  by  their  bitter  or  aftringent 
ffimul.us,  incrcafe  the  adfion  of  the  ftomach,  as  camomile  and 
white  vitriol,  if  their  quantity  isincreafed  above  a certain  dofe, 
become  emetics. 

Thefe  inverted  motions  of  the  ftomach  and  throat  are  gene- 
rally produced  from  the  ftimulus  of  unnatural  food,  and  are 
intended  with  the  fenfation  of  naufea  or  fleknefs : but  as  this 

fenfation 


2®6  OF  THE  STOMACH  Sect. XXV.  7, 8, 9,10. 

ferifation  is  again  conneXed  with  an  idea  of  the  diftafteful 
food,  which  induced  it,  fo  an  idea  of  naufeous  food  will  alfo 
fame  times  excite  the-  action  of  naufea  ; and  that  give  rife,  by  af- 
fociation,  to  the  inve-rlion  of  the  motions  of  the  llomach  and 
throat,  as  fome,  who  have  had  horfe-flefh  or.  dogs-flelh  given 
them  for  beef  or  mutton,  are  faid  to  have  vomited  many  hours 
afterwards,  when  they  have  been  told  of  the  impofuion.  - 

I have  been  tok)  of  a perfon,  who  had  gained  a voluntary 
command  over  thefe  inverted  motions  of  the  ftomach  and  throat, 
and  fupported  himfclf  by  exhibiting  this  curioffty  to  the  pub- 
lic. At  thefe  exhibitions  he  fwallowed  a pint  of  red  rough 
goofeberries,  and  a pint  of  white  fmooth  ones ; brought  them 
up  in  finall  parcels  in  his  mouth,  and  reftored  them  feparately  to 
the  IpeXat'ors,  who  called  for  red  or  white  as  they  pleaied,  til! 
the  whole  were  redelivered. 

7.  At  the  fame  time  that  thefe  motions  of  the  ftomach  and 
fhroatare  ftimulated  into  inverfion,  iome  of  the  other  irritative 
motions,  that  had  acquired  more  immediate  connexions  with  the 
ftomach,  as  thofe  of  the  gaftric  glands,  are  excited  into  ftron- 
ger  aXionby  this  affociation ; and  fome  other  of  thefe  motions, 
which  are  more  eafily  excited,  as  thofe  of  the  gaftric  lympha- 
tics, are  inverted  by  their  affociation  with  the  retrograde  motions 
of  the  ftomach,  and  rigurgitate  their  contents,  and  thus  a greater 
quantity  of  mucus,  and  of  lymph,  or  chyle,  is  poured  into  the 
ftomach,  and  thrown  up  along  with  its  contents. 

8.  Thefe  inverfions  of  the  motions  of  the  ftomach  in  vomit- 
ing are  performed  by  intervals,  for  the  fame  reafon  tint  manv 
other  motions  are  reciprocally  exerted  and  relaxed  ; for  during 
the  time  of  exertion,  the  ftimulus,  or  fenfation  which  caufed 
this  exertion,  is  not  perceived ; but  begins  to  be  perceived  again 
as  foon  as  the  exertion  ceafes,and  is  fome  time  ip  again  produc- 
ing its  effeX,  as  explained  in  SeX.  XXXIV.  on  Volition ; 
where  it  is  (liewn,  that  the  contraX'ons  of  the  fibres,  and  the 
fenfation  of  pain  which  occaffoned  that  exertion,  cannot  exift 
at  the  fame  time.  ' The  exertion  ceafes  from  another  caufe  alfo, 
which  is  the  exhauftion  of  the  fenforial  power  of  the  part,  and 
thefe  two  caufes  frequently  operate  together. 

9.  At  the  times  of  thefe  inverted  efforts  of  the  ftomach,  not 
only  the  lymphatics,  which  open  their  mouths  into  the  ftomach, 
but  thofe  of  the  {kin  alfo,  are  for  a time  inverted  ; for  fweats 
are  iometimes  pufhed  out,  during  the  efforts  of  vomiting,  with- 
out an  increafe  of  heat. 

10.  But  if,  by  a greater  ftimulus,  the  motions  of  the  ftomach 
are  inverted  If  ill  more  violently,  or  more  permanently,  the  duo- 
denum has  its  periftaltic  motions  inverted  at  the  fame  time  by 


£ect.  XXV.  1 1,  i2, 13.  AND  INTESTINES.  207 

their  affociation  with  thofe  of  the  ftomach  ; and  the  bile  and 
pancreatic  juice  which  it  contains,  are,  by  the  inverted  motions, 
brought  up  into  the  ftomach,  and  difcharged  along  with  its  con- 
tents ; while  a greater  quantity  of  bile  and  pancreatic  juice  is 
poured  into  this  intefiine  ; as  the  glands  that  fecrete  them  are,  1 
by  their  affociation  with  the  motions  of  the  intefiine,  excited 
into  flronger  a£fion  than  ufual. 

1 1.  The  other  inceftines  are,  by  affociation,  excited  into  more 
powerful  adtion,  while  the  lymphatics,  that  open  their  mouths 
into  them,  fuffer  an  inverfion  of  their  motions  correfponding- 
with  the  lymphatics  of  the  ftomach  and  duodenum,  which,  with 
a part  of  the  abundant  fecretion  of  bile,  is  carried  downwards, 
and  contributes  both  to  flimulate  the  bowels  and  to  increafe 
the  quantity  of  the  evacuations.  This  inverfion  of  the  motion 
of  the  lymphatics  appears  from  the  quantity  of  chyle,  which 
comes  away  by  fools  ; which  is  otherwife  abforbed  as  foon  as 
produced,  and  by  the  immenfe  quantity  of  thin  fluid  which  is 
evacuated  along  with  it. 

12.  But  if  the  ftimujus,  which  inverts  the  ftomach,  be  ftill 
more  powerful,  or  more  permanent,  it  fometimes  happens  that 
the  motions  of  the  biliary  glands,  and  of  their  excretory  du£ts, 
are,  at  the  fame  time,  inverted,  and  regurgitate  their  contained 
bile  into  the  blood-yeffels,  as  appears  by  the  yellow  colour  of 
the  {kin,  and  of  the  urine ; and  it  is  probable  the  pancreatic  fe- 
cretion may  fuffer  an  inverfion  at  the  fame  time,  though  we 
have  yet  no  mark  by  which  this  can  be  afcertained. 

13.  Mr. eat  two  putrid  pigeons  out  of  a cold  pigeon 

pye,  and  drank  about  a pint  of  beer  and  ale  along  with  them, 
and  immediately  rode  about  five  miles.  He  was  then  feized 
with  vomiting,  which  was  after  a few  periods  fucceeded  by  purg- 
ing; thefe  continued  alternately  for  two  hours ; and  the  purg- 
ing continued,  by  intervals,  for  fix  or  eight  hours  longer.  Dur- 
ing this  time  he  could  not  force  himfelf  to  drink  more  than 
one  pint  in  the  whole.  This  great  inability  to  drink  was  owing 
to  the  naufea,  or  inverted  motions  of  the  ftomach,  which  the 
voluntary  exertion  offwallowing  could  feldom  and  with  diffi- 
culty overcome  ; yet  he  difcharged  in  the  whole  at  leaft  fix 
quarts.  Whencecame  this  quantity  of  liquid  ? Firft,  the  contents 
of  the  ftomach  were  emitted,  then  of  the  duodenum,  gall-blad- 
der, and  pancreas,  by  vomiting.  After  this  the  contents  of  rhe 
lower  bowels,  then  the  chyle  that  was  in  the  ladfeal  veffels 
and  in  the  receptacle  of  chyle,  was  regurgitated  into  the  intef- 
tines  by  a retrograde  motion  of  thefe  veffels.  And  afterward* 
the  mucus  depolited  in  the  cellular  membrane,  and  on  the  fur- 
face  of  all  the  other  membranes,  feems  to  have  been  abforbed  ; 

and 


20$  OF  THE  STOMACH  Sect.  XXV.  14, 15. 

and,  with  the  .fluid  abforbed  from  the  air,  to  have  been  carried 
up  their  refpedive  lymphatic  branches,  by  the  increafed  energy 
mf  their  natural  motions,  and  down  the  vifceral  lymphatics,  or 
ladeals,  by  the  inverfion  of  their  motions. 

14.  It  may  be  difficult  to  invent  experiments  to  demonftrate 
the  truth  of  this  inverfion  of  fome  branches  of  the  abforbent 
dyflern,  and  increafed  ahforption  of  others ; -but  the  analogy  of 
thefe  veffels  to  the  inteftinal  canal,  and  the  fymptoms  of  many 
difeafes,  render  this  opinion  more  probable  than  mamr  other  re- 
ceived  opinions  of  the  animal  economy. 

In  the  above  inftar.ee,  after  the  yellow  excrement  was  void- 
ed, the  fluid  ceafed  to  have  any  fmell,  and  appeared  like  curd- 
led milk,  and  then  a thinner  fluid,  and  fome  mucus,  were  eva- 
cuated. Did  not  tbefefeem  to  partake  of  the  chyle,  of  the  mucus 
fluid  from  ail  the  cells  of  the  body ; and  laftly,  of  the  attnof- 
phere  moifture?  All  thefe  fads  may  bp  eafily  qbferved  by  anr 
one  who  takes  a brifk  purge. 

15.  Where  the  ftimulus  on  the  ftomach,  or  on  fome  other 
part  of  the  inteftinal  canal,  is  ftili  more  permanent,  not  only 
the  ladeal  veffels,  but  the  whole  canal  itfelf,  becomes  inverted 
from  its  affociations-:  this  is  the  iliac  paffion,  in  which  all  the 
fluids  mentioned  above  are  thrown  up  by  the  mouth.  At 
this  time  the  valve  in  the  colon,  from  the  inverted  motions  of 
that  bowel,  and  the  inverted  adion  of  this  living  valve,  docf 
not  prevent  the  regurgitation  of  its  contents. 

The  ftrudure  of  this  valve  may  be  reprefented  by  a flexile 
leathern  pipe  (landing  up  from  the  bottom  of  a veflel  of  wa- 
ter : its  fiues  coilapfe  by  the  preffure  of  the  ambient  fluid,  as 
a fmall  part  of  that  fluid  paffes  through  it;  but  if  it  has  a liv- 
ing power,  and  by  its  inverted  adion  keeps  itfelf  open,  it  be- 
comes like  a rigid  pipe,  and  will  admit  the  whole  liquid  to 
pafs.  See  Sed.  XXIX.  2.  5. 

In  this  cafe  the  patient  is  averfe  to  drink,  from  the  conftant 
inverfion  of  the  motions  of  die  ftomach  ; and  yet  many  quarts 
are  daily  ejected  from  the  ftomach,  which  at  length  fmell  of 
excrement,  and  at  laft  feem  to  be  only  a thin  mucilaginous  or 
Aqueous  liquor. 

From  whence  is  it  poffible,  that  this  great  quantity  of  fluid, 
for  many  fucceflive  days,  can  be  fupplied,  after  the  cells  of  the 
body  have  given  up  their  fluids,  but  from  the  atmolphere  ? 
When  the  cutaneous  branch  of  abforbents  ads  with  unna- 
tural ftrengtb,  it  is  probable  the  inteftinal  branch  has  its  motions 
inverted,  and  thus  a fluid  is  fupplied  without  entering  the  arte- 
rial fyftem.  Could  oiling  or  painting  the  fkingive  a check  ter 
this  difeafe  ? 


AND  INTESTINES, 


&CT.XXV.  16. 


209 


So,  when  the  ftomach  has  its  motions  inverted,  the  lympha- 
tics of  the  ftomach,  which  are  moft  ftridtiy  aftbciated  with  it, 
invert  their  motions  at  the  fame  time.  But  the  more  diftantr 
branches  of  lymphatics,  which  are  lefs  ftridly  aftbciated  with 
it,  a£t  with  increafed  energy ; as  the  cutaneous  lymphatics  in  the- 
cholera,  or  iliac  palfton,  above  defcribed.  And  other  irritative 
motions  become  decreafed,  as  the  pulfations  of  the  arteries,  from- 
the  extra-derivation  or-exhauftion  of  thefenforial  power. 

Sometimes,  -when  ftronger  vomiting  takes  place,  the  more, 
diftant  branches  of  the  lymphatic  fyftem  invert  their  motions 
with  thole  of  the  ftomach,  and  loofe  ftools  are  produced,  and 
cold  fweats. 

So,  when  the  ladteals  have  their  motions  inverted,  as  during 
the  operation  of  ftrong  purges,  the  urinary  and  cutaneous  ab- 
forbents  have  their  motions  increafed,  to  fupply  the  want  of 
fluid  in  the  blood,  as  in  great  thirft ; but  after  a meal,  with; 
fufficicnt  potation,  the  urine  is  pale ; that  is,  the  urinary  abforb- 
ents a£t  weakly,  no  fupply  of  water  being  wanted  for  the 
blood.  And  when-  the  inteftinal  abforbents  add  too  violently,, 
as  when,  too  great  quantities  of  fluid  have  been  drank,  the. 
urinary  abforbents  invert  their  motions  to  carry  off  the  fuper- 
fluiry,  which-  is  a new  cireumftance  of  affociation,  and  a 
temporary  diabetes  fupervenes. 

1 6.  I have  had  the  opportunity  of  feeing  four  patients  its 
the  iliac  paflion,  where  the  ejedted  material  fmelled  and  look- 
ed like  excrement.  Two  of  thefe  were  fo  exhaufted  at  the 
time  I faw  them,  that  more  blood  could  not  be  taken  from- 
them ; and  as  their  pain  had  ceafed,  and  they  continued  to  vo- 
mit up  every  thing  which  they  drank,  I fulpecled  that  a mor- 
tification of  the  bowel  had  already  taken  place  ; and  as  thev 
were  both  women-  advanced  in  life,  and  a mortification  is  pro- 
duced with  lefs  preceding  pain  in  old  and  weak  people,  thefe 
both  died.  The  other  two,  who  were  both  young  men,  had 
ftill  pain  and  ftrength  fufficient  for  further  veneledlion,  and 
they  neither  of  them  had  any  appearance  of  hernia  ; both  re- 
covered by  repeated  bleeding,  and  a fcruple  of  calomel  given 
to  one,  and  half  a dram  to  the  other,  in  very  fmall  pills : the 
ufual  means  of  elyfters,  and  purges,  joined  with  opiates,  had 
been  in  vain  attempted.  I have  thought  an  ounce  or  two  of 
crude  mercury  in  lefs  violent  difeafes  of  this  kind  has  been  of 
ufe,  by  contributing  to  reftore  its  natural  motion  to  fome  part 
of  the  inteftinal  canal,  either  by  its  weight  or  ftimuius ; and 
that  hence  the  whole  tube  recovered  its  ufual  affociationS  of 
progreflive  periftaltic  motion.  I have  in  three  cafes  feen  crude 
mercury  given  in  fmall  dofes,  as  one  or  two  ounces,  twice  a 
day,  have  great  effect  in  flopping  pertinaceous  vomiting. 

17.  Beftdcs 


2 io  OF  THE  STOMACH,  See.  Sect.  XXV.  17. 

17.  Befides  the  affections  above  deferibed,  the  ftomach  is 
liable,  like  many  other  membranes  of  the  body,  to  torpor,  with- 
out confequent  inflammation  ; as  happens  to  the  membranes 
about  the  head  in  fome  cafes  of  hemicrania,  or  in  general 
headaeh.  This  torpor  of  the  ftomach  is  attended  with  indi- 
geftion,  and  confequent  flatulency,  and  with  pain,  which  is 
ufually  called  the  cramp  of  the  ftomach,  and  is  relievable  by 
aromatics,  effential  oils,  alcohol,  or  opium. 

The  intrufion  of  a gall-ftone  into  the  common  bile-du£t, 
from  the  gall-bladder,  is  fometimes  miftaken  for  a pain  of  the 
ftomach,  as  neither  of  them  are  attended  with  fever ; but  in  the 
paffage  of  a gall-ftone,  the  pain  is  confined  to  a lefs  fpace, 
which  is  exaftly  where  the  bile-dudt  enters  the  duodenum,  as 
explained  in  SeCtion  XXX.  3.  Whereas,  in  this  gaftrodvnia 
the  pain  is  diffufed  over  the  whole  ftomach  ; and,  like  other 
difeafes  from  torpor,  the  pulfe  is  weaker,  a-nd  the  extremities 
colder,  and  the  general  debility  greater  than  in  the  paffage 
of  a gall-ftone  ; for  in  the  former  the  debility  is  the  coni'e- 
quence  of  the  pain,  in  the  latter  it  is  the  caufe  of  it. 

Though  the  firft  fits  of  the  gout,  I believe,  commence  with 
a torpor  of  the  liver ; and  the  ball  of  the  toe  becomes  inflam- 
ed, inftead  of  the  membranes  of  the  liver,  in  confequence  of  this 
torpor,  as  a coryza  or  catarrh  frequently  fuccecds  a long  ex- 
pofuie  of  the  feet  to  cold,  as  in  l'now,  or  on  a moift  brick- 
floor;  yet  in  old  or  exhaufted  conftitutions,  which  have  been 
long  habituated  to  its  attacks,  it  fometimes  commences  with  a 
torpor  of  the  ftomach,  and  is  transferable  to  every  membrane 
of  the  body.  When  the  gout  begins  with  torpor  of  the  fto- 
mach, a painful  fenfation  of  cold  occurs,  which  the  patient 
compares  to  ice,  with  weak  pulfe,  cold  extremities,  and  fick- 
nefs  ; this,  in  its  {lighter  degree,  is  relievable  by  fpice,  wine,  or 
opium  ; in  its  greater  degree  it  is  fucceeded  by  ludden  death, 
which  is  owing  to  the  fympathy  of  the  ftomach  with  the 
heart,  as  explained  below. 

If  the  ftomach  becomes  inflamed  in  confequence  of  this  gou- 
tv  torpor  of  it,  or  in  confequence  of  its  fympathy  with  lome 
other  part,  the  danger  is  lefs.  A licknefs  and  vomiting  conti- 
nues many  davs,  or  even  weeks,  the  ftomach  rejecting  every- 
thing ftimulant,  even  opium  or  alcohol,  together  with  much 
vifeid  mucus,  till  the  inflammation  at  length  ceafes,  as  hap- 
pens when  other  membranes,  as  thofe  of  the  joints,  are  the  feat 
ot  gouty  inflammation,  as  obferved  in  Sect.  XXIV.  2.  8. 

The  fympathy,  or  affociation  of  motions,  between  thofe 
of  the  ftomach  and  thofe  of  the  heart,  are  evinced  in  many 
difeales.  Firft,  many  people  are  occaiionally  affected  with  ar. 

intermiflioR 


Sect.  XXVI.  GLANDS  AND  MEMBRANES.  2 1 1 


intermiffion  of  their  pulfe  for  a few  days,  which  then  ceafes 
again.  ]n  this  cafe  there  is  a flop  of  the  motion  of  the  heart, 
and  at  the  fame  time  a tendency  to  erudation  from  the  ftomach. 
As  foon  as  the  patient  feels  a tendency  to  the  intermiffion  of 
the  motion  of  his  heart,  if  he  voluntarily  brings  up  wind  from 
his  ftomach,  the  ftop  of  the  heart  does  not  occur.  From  hence 
I conclude,  that  the  ftop  of  digeftion  is  the  primary  difeafe ; and 
drat  air  is  inftantly  generated  from  the  aliment,  which  begins 
to  ferment,  if  the  digeftive  procefs  is  impeded  for  a moment, 
(fee  Sed.  XXIII.  4.)  and  that  the  ftop  of  the  heart  is  in  con- 
fequence  of  the  afl'cciation  of  the  motions  of  thefe  vifeera,  as 
explained  in  Sed.  XXXV  1.  4.  but  if  the  little  air.  which  is 
inftantly  generated  during  the  temporary  torpor  of  the  ftomach, 
be  evacuated,  the  digeftion  recommences,  and  the  temporary 
torpor  of  the  heart  does  not  follow.  One  patient,  whom  I 
lately  faw,  and  who  had  been  for  five  or  fix  days  much  trou- 
bled with  this  intermiffion  of  a pulfation  of  his  heart,  and  who 
had  hemicrania,  with  fome  lever,  was  immediately  relieved  from 
them  all  by  lofing  ten  ounces  of  blood,  which  had  what  is  term- 
ed an  inflammatory  cruft  on  it. 

Another  inftance  of  this  afiociation  between  the  motions  of 
t'he  ftomach  and  heart  is  evinced,  by  the  exhibition  of  an  over- 
dofe  of  foxglove,  which  induces  an  inceftant  vomiting,  which 
is  attended  with  very  flow,  and  fometimes  intermitting  pulfe  ; 
which  continues,  in  fpite  of  the  exhibition  of  wine  and  opium, 
for  two  or  three  days.  To  the  fame  affociation  muft  be  a- 
feribed  the  weak  pulfe,  which  conftantly  attends  the  exhibition 
of  emetics  during  their  operation.  And  alfo  the  fudden  deaths, 
which  have  been  occafioned  in  boxing  by  a blow  on  the  fto- 
mach ; and  laftly,  the  fudden  death  of  thofe  who  have  been 
long  debilitated  by  the  gout,  from  the  torpor  of  the  ftomach. 
See  Sed.  XXV.  1.  4. 

— ■raTisg’r^Bw— 

SECT.  XXVI. 

OF  THE  CAPILLARY  GLANDS  AND  MEMBRANES. 

I.  1.  The  capillary  vcffcls  are  glands.  2.  Their  excretory 
dutls.  Experiments  on  the  mucus  of  the  intcjlines , ab- 
domen, cellular  membrane,  and  on  the  humours  of  the 
eye.  3.  Scurf  on  the  head , cough,  catarrh,  diarrhoea , 
gonorrhoea.  4.  Rheumatifm.  Gout.  Leprofy.  II.  1. 
The  mojl  minute  membranes  are  unorgan'vzed.  2.  Lar- 
ger membranes  are  compofed  of  the  dudts  of  the  capilla- 
F f ries , 


2i2  GLANDS  AND  MEMBRANES.  Sect.  XXVI.  i. 


ries,  and  the  mouths  of  the  abforbcmts. 
fluid  is  ferreted  on  their  furfaces.  III. 
rheumatifm. 


3.  Mucilaginous 
Three  kinds  of 


1.  1.  THE  capillary  veffels  are  like  all  the  other  glands 
except  the  abiorbent  fyftem,  inafnriuch  as  they  receive  bicod 
from  the  arteries,  feparate  a fluid  from  it,  and  return  the  re- 
mainder by  the  veins. 

2.  This  feries  of  glands  is  of  the  rr,o(l  extenfive  ufe,  as 
their  excretory  duels  oren  on  the  whole  external  Ikin,  forming 
its  perlpirative  pores,  and  on  the  internal  furfaces  of  every 
cavity  of  the  body.  Their  iecretion  on  the  Ikin  is  termed  in- 
fallible perforation,  which  in  health  is  in  part  reabforbed  by 
the  mouths  of  the  lymphatics,  and  in  part  evaporated  in  the 
air:  the  fecreticn  on  the  membranes,  which  line  the  larger 
cavities  ot  the  body,  which  have  external  openings,  as  the 
mouth  and  inteflinal  canal,  is  termed  mucus,  but  is  not  how- 
ever coagulable  by  heat ; and  the  iecretion  on  the  membianes 
of  thole  cavities  of  the  bodv,  which  have  no  external  open- 
ings, is  called  lymph,  or  water,  as  in  the  cavities  ot  the  cellu- 
lar membrane,  and  of  the  abdomen:  this  lymph,  however,  is 
coagulable  by  the  heat  of  boiling  water.  Some  mucus,  nearly 
as  vifeid  as  the  white  of  egg,  which  was  difeharged  by  ftool, 
did  not  coagulate,  though  1 evaporated  it  to  one  fourth  of  the 
quantity  ; nor  did  the  aqueous  and  vitreous  humours  of  a 
fheep’s  eye  coagulate  by  the  like  experiment : but  the  ferofity 
from  an  anafarcous  leg,  and  that  from  the  abdomen  of  a drop- 
fical  perfon,  and  the  cryftalline  humour  of  a fheep’s  eye,  co- 
agulated in  the  fame  heat. 

3.  When  any  of  thefe  capillary  glands  are  llimulated  into 
greater  irritative  adlions  than  is  natural,  they  fecrete  a more 
copious  material;  and  as  the  mouths  ot  the  abiorbent  fvfteni, 
which  open  in  their  vicinity,  are  at  the  fame  time  llimulated 
into  greater  action,  the  thinner  and  more  faline  part  of  the  fe- 
ereted fluid  is  taken  up  again;  and  tire  remainder  is  not  only 
more  copious,  but  alio  more  vifeid  than  natural.  This  is  more 
or  lefs  troublefome,  or  noxious,  according  to  the  importance 
of  the  functions  ot  the  part  affected : on  the  Ikin  and  bronchia?, 
where  this  fecretic  n ought  naturally  to  evaporate,  it  becomes 
fo  vifeid  as  to  adhere  to  the  membrane ; on  the  tongue  it  forms 
a pellicle,  which  can  with  difficulty  be  feraped  off ; produces 
the  feurf  on  the  heads  of  many  people;  and  the  mucus,  which 
is  fpit  up  by  others  in  coughing.  On  the  notlrils  and  fauces, 
when  tire  iecretion  of  thefe  capillary  glands  is  increaled,  it  is 
termed  Ample  catarrh ; when  in  die  inteftines,  a mucus  diarr- 
hoea; 


Sect.  XXVI.  2.  GLANDS  AND  MEMBRANES.  213 

hcea  ; and  in  the  urethra,  or  vagina,  it  has  the  name  of  go- 
norrhoea, or  fluor  albus. 

4.  When  thefe  capillary  glands  become  inflamed,  a ft  ill 
more  vifcid,  or  even  cretaceous  humour  is  produced  upon  the 
furface  of  the  membranes,  which  is  the  caufe  or  the  effect  of 
rheumatifm,  gout,  leprofy,  and  of  hard  tumours  of  the  legs, 
which  are  generally  termed  fcorbutic ; all  which  will  be  treat- 
ed of  hereafter. 

JL  1.  The  whole  furface  of  the  bo  'y,  with  all  its  cavities 
and  contents,  is  covered  with  membrane.  It  lines  every  vef- 
fel,  forms  every  cell,  and  binds  together  all  the  mufcular  and 
perhaps  ofleous  fibres  of  the  body;  and  is  itfelf  therefore  pro- 
bably a Ampler  fubftance  than  thofe  fibres.  And  as  the  con- 
taining vetfels  of  the  body,  from  the  largeft  to  the  leaft,  are  thus 
lined  and  connedted  with  membranes,  it  follows,  that  thefe  mem- 
branes rfiemfelves  confifted  of  unorganized  materials. 

For  however  fmall  we  may  conceive  the  diameters  of  the 
■minuteft  veflels  of  the  body,  which  efcape  our  eyes  and  glafies, 
yet  thefe  veffels  muft  confift  of  coats  or  tides,  which  are  made 
up  of  an  unorganized  material,  and  which  are  probably  pro- 
duced from  a gluten,  which  hardens  after  its  production,  like 
the  lilk  or  web  of  caterpillars  and  fpiders.  Of  this  material 
confift  the  membranes,  which  line  the  /hells  of  eggs,  and  the 
/hell  itfelf;  both  which  are  unorganized,  and  are  formed  from 
mucus,  which  hardens  after  it  is  formed,  either  by  the  ahforp- 
tion  of  its  more  fluid  part,  or  by  its  uniting  with  feme  part  of 
the  atmofphere.  Such  is  alfo  the  production  of  the  thel'ls  of 
Avails,  and  of  fliell-fifh,  and  I feppoie  of  the  enamel  of  the  teeth. 

2.  But  though  the  membranes  that  compote  the  tides  of  the 
moft  minute  veflels,  are,  in  truth,  unorganized  materials ; yet 
the  larger  membranes,  which  are  perceptible  to  the  eye,  feem 
to  be  compofed  of  an  intertexture  of  the  mouths  of  the  ab- 
ferbent  fyftem,  and  of  the  excretory  dudts  of  the  capillaries, 
with  their  concomitant  arteries,  veins,  and  nerves:  and  from 
this  conftruction  it  is  evident,  that  thefe  membranes  muft  poflefs 
great  irritability  to  peculiar  ftimuli,  though  they  are  incapable 
of  any  motions  that  are  vifible  to  the  naked  eye : and  daily  ex- 
perience {hews  us,  that  in  their  inflamed  ftate  they  have  the 
greateft  fenflbility  to  pain,  as  in  tire  pleurify  and  paronychia. 

3.  On  all  thefe  membranes  a mucilaginous  or  aqueous  fluid 
is  fecreted,  which  moiftens  and  lubricates  their  furfaces,  as  was 
explained  in  Sedtion  XXIII.  2.  Some  have  doubted,  whether 
this  mucus  is  feparatcd  from  the  blood  by  an  appropriated  fet 
of  glands,  or  exudes  through  the  membranes,  or  is  an  abra- 
ficn  or  deftruction  of  the  furface  of  the  membrane  itfelf,  which 

is 


214 


OF  HEMORRHAGES. 


Sect.  XXVII. 


is  continually  repaired  on  the  other  fide  of  it;  but  the  great  ana- 
logy between  the  capillary  veftels,  and  the  other  glands,  coun- 
tenances .the  former  opinion,  and  evinces,  that  thefe  capilla- 
ries are  the  glands  that  fecrete  it;  to  which  we  muft  add.  that 
the  blood,  in  paffing  thefe  capillary  veffels.  undergoes  a change 
in  its  colour,  from  florid  to  purple,  and  gives  out  a quantity  of 
heat;  from  whence,  as  in  other  glands,  we  muft  conclude  that 
fomething  is  fecreted  from  it. 

III.  T'he  feat  of  rheumatifm  is  in  the  membranes,  or  upon 
them;  but  there  are  three  very  uiftinfl  difeafes,  which  com-  ' 
monly  are  confounded  under  this  name.  Firft,  when  a mem- 
brane becomes  afte-Ted  with  torpor,  or  inactivity  of  the  veft 
fels  which  compoie  it,  pain  aril  coldnefs  fucceed,  as  in  the 
hemicrania,  and  other  head-achs,  which  are  generally  termed 
nervous  rheumatifm ; they  exift  whether  the  part  be  at  reft  or 
in  motion,  and  are  generally  attended  with  other  marks  of  de- 
bility.' 

Another  rheumatifm  is  faid  to  exift,  when  inflammation 
and  fweliing,  as  well  as  pain,  a fie  ft  foine  of  the  membranes  ’ 
of  the  joints,  as  of  the  ancles,  wrifts,  kuees,  elbows,  and 
fometimes  of  the  ribs.  This  is  accompanied  with  fever,  is 
analogous  to  p'eurify,  and  other  inflammations,  and  is  termed 
'the  acute  rheumatifm. 

A third  difeafe  is  called  chronic  rheumatifm,  which  is  dif-J 
tinguifhed  from  that  firft  mentioned,  as  in  this  the  pain  only  p 
a ftedts  the  patient  during  the  motion  of  the  part,  and  from  the 
iecond  kind  of  rheumatifm  above  deferibed,  as  it  is  not  attend- 1 
ed  with  quick  pulfe  or  inflammation.  It  is  generally  believed 
to  fucceed  the  acute  rheumatifm  of  the  fame  part,  ar.d  mat 
fome  coagulable  lymph,  or  cretaceous,  or  calculous  material,  . 
has  been  left  on  the  membrane ; which  gives  pain,  when  the 
mufeies  move  over  it,  as  fome  extraneous  body  would  do,  • ' 
which  was  too  infoluble  to  be  abforbed.  Hence  there  is  an 
analogy  between  this  chronic  rheumatifm  and  the  difeafes 
which  produce  gravel  or  gout-ftones  ; and  it  may  perhaps  rc-y 
ceive  relief  from  the  fame  remedies,  fuch  as  aerated  fal  foda.  1 


SECT.  XXVII. 

OF  HEMORRHAGES. 

I.  The  veins  are  ah  [orient  vejfe'ls.  I.  Hemorrhages  fieri 
inflammation.  Cafe  of  hemorrhage  from  the  kidney  cur- 
ed by  cold  bathing.  Cafe  of  hemorrhage  from  the  nof; 
curcd  by  cold  immerfsn.  II.  Hemorrhage  from  Venous 

parahfs . 


Sect.  XXVII.  i.  OF  HAEMORRHAGES. 


215 

paralyfs.  Of  Piles.  Black  fools.  Petechia.  Confump- 
tion.  Scurvey  of  the  lungs.  B/ackncfs  of  the  face  and 
eyes  in  epileptic  fits.  Cure  of  haemorrhages  from  venous 
inability. 

I.  AS  the  imbibing  mouths  of  the  abforbent  fyftem  already 
deferibed  open  on  the  furface,  and  into  the  larger  cavities  of 
the  body,  fo  there  is  another  fyftem  of  abforbent  veffels,  which 
are  not  commonly  efteemed  iuch ; I mean  the  veins,  which 
take  up  the  blood  from  the  various  glands  and  capillaries,  after 
their  proper  fluids  or  fecretions  have  been  ieparated  from  it. 

The  veins  referable  the  other  abforbent  veffels;  as  the  pro- 
greflfion  of  their  contents  is  carried  on  in  the  fame  manner  in 
both,  they  alike  abforb  their  appropriated  fluids,  and  have 
valves  to  prevent  its  regurgitation  by  the  accidents  of  mecha- 
nical violence.  This  appears,  flrft,  becaufe  there  is  no  pulia- 
tion in  the  very  beginnings  ot  the  veins,  as  is  feen  by  micro- 
fcopes;  which  mud  happen,  if  the  blood  was  carried  into 
them  by  the  attion  of  the  arteries.  For  though,  the  con- 
currence of  various  venous  ilreams  of  blood  from  different 
diftances  mud  prevent  any  pulfation  in  the  larger  branches, 
yet,  in  the  very  beginnings  of  all  thefe  branches,  a pulfation 
muft  unavoidably  exift,  it  the  circulation  in  them  was  owing 
to  the  intermitted  force  of  the  arteries.  Secondly,  the  venous 
abforption  of  blood  from  the  penis,  and  from  the  teats  of  fe- 
male animals  after  their  erection,  is  {till  more  fimilar  to  the 
lymphatic  abforption,  as  it  is  previoufly  poured  into  cells, 
where  all  arterial  impulfe  muftceafe. 

There  is  an  experiment,  which  feems  to  evince  this  venou>s 
abforption,  which  confilts  in  the  external  application  of  a ftimu- 
lus  to  the  lips,  as  of  vinegar,  by  which  they  become  inflantly 
pale;  that  is,  the  bibulous  mouths  of  the  veins  by  this  Annu- 
lus are  excited  to  abforb  the  blood  fafter  than  it  can  be  fup- 
plied  by  the  ufual  arterial  exertion.  See  Sett.  XXIII.  5. 

There  are  two  kinds  of  haemorrhages  frequent  in  difeafes  ; 
one  is  where  the  glandular  or  capillary  attion  is  too  power- 
fully exerted,  and  propels  the  blood  forwards  more  haftily 
than  the  veins  can  abforb  it;  and  the  other  is,  where  the  ab- 
forbent power  of  the  veins  is  diminifhed,  or  a branch  of  them 
is  become  totally  paralytic. 

The  former  ot  thefe  cafes  is  known  by  the  heat  of  the  part, 
and  the  general  fever,  or  inflammation  that  accompanies  the 
haemorrhage.  An  haemorrhage  from  thenofe  or  from  the  lungs 
is  fometimes  a cribs  of  inflammatory  difeafes,  as  of  die  hepati- 
tis and  gout,  and  generally  eeafes  fpontaneoufly,  when  the  vef- 
fels 


2l6 


OF  HAEMORRHAGES.  Sect.  XXVII.  2. 


felsare  confiderably  emptied.  Sometimes  the  haemorrhage  re- 
curs by  daily  periods,  accompanying  the  hot  fits  of  fever,  and 
ceafingin  the  cold  fits,  or  in  the  iniermiffions.  This  is  to  be  cur- 
ed by  removing  the  febrile  paroxvfms,  which  will  be  treated 
of  in  their  place.  .Otherwife  it  is  cured  bv  venefection,  by 
the  internal  or  external  preparations  of  lead,  or  by  the  applica- 
tion of  cold,  with  an  abftemious  diet  and  diluting  liquids,  like 
other  inflammations;  which,  by  inducing  a quielcence  on 
thoie  glandular  parts  that  are  affiedied,  prevents  a greater  quan- 
tity of  blood  from  being  protruded  forwards  than  the  veins  are 
capable  of  abforbing. 

Mr.  B had  an  haemorrhage  from  his  kidney,  and  parted 

with  not  lefs  than  a pint  of  blood  a day  (by  conjedfure)  along 
with  his  urine,  for  above  a fortnight;  venefections,  mucilages, 
balfams,  preparations  of  lead,  the  hark,  alum,  and  dragon’s 
blood,  opiates,  with  a large  blifter  on  his  loins,  were  feparateir 
tried,  in  large  dofes,  to  no  purpofe.  He  was  then  directed  to 
bathe  in  a cold  fpring  up  to  the  middle  of  his  body  only,  the 
upper  part  being  covered,  and  the  haemorrhage  dim  ini  filed  at 
the  firli,  and  ceal'ed  at  the  fecond  immerfion. 

In  this  cafe  the  external  capillaries  were  rendered  quiefeent 
by  the  coldnefsof  the  water,  and  thence  a lefs  quantity  of  '.flood 
was  circulated  through  them  ; and  the  internal  capillaries,  or 
ether  glands,  became  quiefeent  from  their  irritative  affociations 
•with  the  external  ones;  and  the  haemorrhage  was  flopped  a 
{efficient  time  for  the  ruptured  veflfels  to  contract  their  aper- 
tures, or  for  the  Wood  in  thofe  apertures  to  coagulate. 

Airs.  K — had  a continued  haemorrhage  from  her  nnfe 

for  fome  days ; the  ruptured  vefTel  was  not  to  be  reached  by 
plugs  up  the  noftrils,  and  the  lenfibility  of  her  fauces  was  luch 
that  nothing  could  be  borne  behind  the  uvula. ' After  repeated 
venefedfion,  and  other  common  applications,  fhe  was  directed 
to  immerfe  her  whole  head  into  a pail  of  water,  which  was 
made  colder  by  the  addition  of  feveral  handfulls  of  fait,  and  the 
haemorrhage  immediately  ceafed,  and  returned  no  more ; hut 
her  pul fe  continued  hard;  and  fine  was  necefliated  to  lofie  blood 
from  the  arm  on  the  fucceeding  day. 

Query.  Might  not  the  cold  bath  inftantly  ftop  haemorrhages 
from  the  lungs  in  inflammatory  cafes  ? for  the  fhortnefs  of 
breath  of  thofe,  who  go  fuddenly  into  cold  water,  is  not  owing 
to  the  accumulation  of  blood  in  the  lungs,  but  to  the  quieficeu-ce 
of  the  pulmonary  capillaries  from  aflbeiation,  as  explained  in 
Sedion  XXXII.  3.  2. 

11.  The  other  kind  of  haemorrhage  is  known  from  its  being 
attended  with  a weak  pull'e,  and  other  iymptoms  of  general  de- 

biiitv. 


Sect.  XXVII.  2. 


HAEMORRHAGES. 


217 

bility,  and  very  frequently  occurs  in  thofe  who  have  difeafed 
livers,  owing  to  intemperance  in  the  ufe  of  fermented  liquors. 
Thefe  conftitutions  are  (hewn  to  be  liable  to  paralyfis  of  the 
lymphatic  abforbents,  producing  the  various  kinds  of  droplles 
in  Se£tion  XXIX.  5.  Now,  if  any  branch  of  the  venous  fyftem 
lofes  its  power  of  abiorption,  the  part  fwells,  and  at  length 
builds  and  dii'charges  the  blood,  which  the  capillaries  or  other 
glands  circulate  through  them. 

- It  fometimes  happens  that  the  large  external  veins  of  the  legs 
burld,  and  effule  their  blood;  but  this  occurs  mold  frequently  in 
the  veins  of  the  inteftines,  as  the  vena  portarum  is  liable  to  fufFer 
from  a fchirus  of  the  liver  oppofing  the  progreffion  of  the  blood, 
which  is  abforbed  from  the  inteihir.es.  Hence  the  piles  are  a 
fymptom  of  hepatic  cbftrudtion ; and  hence  the  copious  difchar- 
ges,  downwards  or  upwards,  of  a black  material,  which  has  been 
called  melancholia,  or  black  bile ; but  is  no  other  than  the  blood 
which  is  probably  difcharged  from  the  veins  of  the  inteftines. 

J.  F.  Meckel,  in  his  Experimenta  de  Finibus  Vaforum, 
publifhed  at  Berlin,  1772,  mentions  his  difcovery  of  a com- 
munication of  a lymphatic  vefTel  with  thegaftric  branch  ®f  th« 
vena  portarum.  It  is  pofiible,  that  when  the  motion  of  the  lym- 
phatic becomes  retrograde  in  feme  difeafes,  that  blood  may  ob- 
tain a pafiage  into  it,  where  it  anaftomofes  with  the  vein,  and 
thus  be  poured  into  the  inteftines.  A difcharge  of  blood  with 
the  urine  fometimes  attends  diabetes,  and  may  have  its  fource 
in  the  lame  manner. 

Mr.  A , who  had  been  a hard  drinker,  and  had  die 

gutta  rofacea  on  his  face  and  breaft,  after  a ftroke  of  the  pally, 
voided  near  a quart  of  a black  vifcid  material  by  ftool ; on  dilut- 
ing it  with  water  it  did  not  become  yellow,  as  it  muff  have  done 
if  it  had  been  inlpiflated  bile,  but  continued  black  like  the  grounds 
of  coffee. 

But  any  other  part  of  the  venous  fyftem  may  become  quie- 
fcent,  or  totally  paralytic,  as  well  as  the  veins  of  the  inteftines  i 
all  which  occur  more  frequently  in  thofe  wrho  have  difeafed 
livers,  than  in  any  other.  Hence  troublefome  bleedings  of  the 
nofe,  or  from  the  lungs  with  a weak  pulfe;  hence  haemorrha- 
ges from  the  kidneys,  too  great  menftruation  ; and  hence  the 
oozing  of  blood  from  every  part  of  the  body,  and  the  petechias 
in  thofe  fevers,  which  are  termed  putrid,  and  which  is  errone- 
oufly  afcribed  to  the  thinnefs  of  the  blood : for  the  blood  in  in- 
flammatory difeafes  is  equally  fluid  before  it  coagulates  in  the 
cold  air. 

Is  not  that  hereditary  confumption,  which  occurs  chiefly  in, 
dark-eyed  people  about  the  age  of  twenty,  and  commences  with 

flight 


2l8 


HAEMORRHAGES.  Sect.  XXVI  f.  sr; 


flight  pulmonary  haemorrhages  without  fever,  a difeafe  of  this 
kind  ? — Thefe  haemorrhages  frequently  begin  during  fleep, 
when  the  irritability  of  the  lungs  is  not  fufficient  in  thefe  pa- 
tients to  carry  on  the  circulation  without  the  afliftance  of  voli- 
tion; for  in  our  waking  hours,  the  motions  of  the  lungs  are  in 
part  voluntary,  efpecially  if  any  difficulty  of  breathing  renders 
the  efforts  of  volition  neceffary.  See  ClafsI.  2.  1.2.  and  Ciafs 
III.  2.  1.  10.  Another  fpecies  of  pulmonary  confumptior,, 
which  fecms  more  certainly  of  fcrophulous  origin,  is  defer:  • ed 
in  the  next  Seftion.  No.  2. 

I have  leen  two  cafes  of  women,  of  about  forty  years  of  age,  j 
both  of  whom  were  feized  with  quick  weak  pulfe,  with  diffi- 
cult refpiration,  and  who  fpit  up.  bv  coughing,  much  vifeid  mu- 
cus mixed  with  dark  coloured  blood.  They  had  both  larce 
vibices  on  their  limbs,  and  petechias ; in  one  the  feet  were  in 
danger  of  mortification,  in  the  other  the  legs  were  cedematous. 
To  relieve  the  difficult  refpiration,  about  fix  ounces  of  blood 
were  taken  from  one  of  them,  which,  to  my  iurprife,  was  fizy, 
like  inflamed  blood : they  had  both  palpitations  or  unequal  pul- 
fations  of  the  heart.  They  continued  tour  or  five  weeks  with 
pale  and  bloated  countenances,  and  did  not  ceafe  fpitting  phlegm 
mixed  with  black  blood,  and  the  pulfe  feldom  flower  than  130 
or  135  in  a minute.  This  blood,  from  its  dark  colour,  and 
from  the  many  vibices  and  petechias,  feems  to  have  been  ve- 
nous blood ; the  quicknefs  of  the  pulfe,  and  the  irregularity  of 
the  motion  of  the  heart,  are  to  be  aferibed  to  debilitv  of  that 
part  of  the  fyflem  ; as  the  extravafation  of  blood  originated  from 
the  defedf  of  venous  abforptiou.  The  approximation  of  thefe 
two  cafes  to  fea-feurvy  is  peculiar,  and  may  allow  them  to  be 
called  fcorbutus  pulmonalis.  Had  thefe  been  younger  fubjeefs, 
and  the  paralylis  of  the  veins  had  only  affedfed  the  lungs,  it  is 
probable  the  difeafe  would  have  been  a pulmonary  confumption. 

Laft  week  I law  a gentleman  of  Birmingham,  who  had  for 
ten  days  laboured  under  great  palpitation  of  his  heart,  which  was 
fo  diflindfly  felt  by  the  hand,  as  to  difcountenance  the  idea  of 
there  being  a fluid  in  the  pericardium.  He  frequendv  fpit  up 
mucus,  ftained  with  dark  coloured  blood ; "his  pulfe  very  une- 
qual and  very  weak,  with  cold  hands  and  nofe.  He  could  not 
lie  down  at  all,  and  for  about  ten  days  paft  could  not  fleep  a 
minute  together,  but  waked  perpetually  with  great  unealinefs. 
Could  thefe  fymptoms  be  owing  to  very  extenflve  adhefions  of 
the  lungs  ? or  is  this  a fcorbutus  pulmonalis  ? After  a few  days 
he  fuddenly  got  fo  much  better  as  to  be  able  to  fleep  many  hours 
at  a time,  by  the  ufe  of  one  grain  of  powder  ot  foxglove  twice 
a.  day,  and  a grain  of  opium  at  night.  After  a few  days  longer, 


Sect.  XXVIII.  i.  ABSORBENT  SYSTEM. 


219 

the  bark  was  exhibited,  and  the  opium  continued  with  fome 
wine  ; and  the  palpitations  of  his  heart  became  much  relieved, 
and  he  recovered  his  ufual  degree  of  health. 

. In  epileptic  fits  the  patients  frequently  become  black  in  the 
face,  from  the  temporary  paralyfis  of  the  venous  fyftem  of  this 
part.  I have  known  two  inftances  where  the  blacknefs  has 

continued  many  days.  M.  P- , who  had  drank  intem- 

perately,  was  feized  with  the  epilepfy  when  he  was  in  his  for- 
tieth year;  in  one  of  thefe  fits  the  white  part  of  Inis  eyes  was 
left  totally  black  with  elfufed  blood;  which  was  attended  with 
no  pain  or  heat,  and  was  in  a few  weeks  gradually  abforbed, 
changing  colour  as  is  ufual  with  vibices  from  bruiles. 

The  hemorrhage  produced  from  the  inability  of  the  veins  to 
ablorb  the  refluent  blood,  is  cured  by  opium,  the  preparations  of 
lteel,  lead,  the  bark,  vitriolic  acid,  and  biifters ; but  thefe  have 
the  effedt  with  much  more  certainty,  if  a venefedtion  to  a few 
ounces,  and  a moderate  cathartic,  with  four  or  fix  grains  of 
calomel,  be  premifed,  where  the  patient  is  not  already  too  much 
dibilitated  ; as  one  great  means  of  promoting  the  ablorption  of 
any  fluid  confifts  in  previoufly  emptying  the  veffeis  which  are 
to  receive  it. 


SECT.  XXVIII. 

OF  THE  PARALYSIS  OF  THE  ABSORBENT  SYSTEM. 

I.  Paralyfis  of  the  laffcals,  atrophy.  Difafe  to  animal  food. 
II.  Caufe  of  dropfy.  Caufe  of  herpes.  Mefntcric  con- 
fumption.  Pulmonary  confumption.  IV hy  ulcers  in  the 
lungs  are  fo  difficult  to  heal. 

THE  term  paralyfis  has  generally  been  ufed  to  exprefs  the 
lofs  of  voluntary  motion,  as  in  the  hemiplagia,  but  may  with 
equal  propriety  be  applied  to  expreis  the  diiobediency  of  the 
mufcular  fibres  to  the  other  kinds  of  flimulus  ; as  to  thofe  of 
irritation  or  fenfation. 

I.  There  is  a fpecies  of  atrophy,  which  has  not  been  well 
underllood ; when  the  abferbent  veffeis  of  the  ftomach  and 
inteftineshave  been  long  inured  to  the  flimulus  of  too  much  fpi- 
rituous  liquor,  they  at  length,  either  by  the  too  hidden  omifTion 
of  fermented  or  fpirituous  potation,  or  from  the  gradual  decay 
of  nature,  become  in  a certain  degree  paralytic : now,  it  is  ob- 
ferved  in  the  larger  mufcles  of  the  body,  when  one  fide  is  pa- 
ralytic, the  other  is  more  frequently  in  motion,  owing  to  the  lets 
expenditure  of  feniorial  power  in  the  paralytic  limbs  ; fo,  in  this 
cafe,  the  other  part  of  the  abforbent  fyftem  acts  with  greater 

G g force. 


220 


PARALYSIS  OF  Sect.  XXVIII.  2. 


force,  or  with  greater  perfeverance,  in  conference  of  the  pa- 
ralyfis  of  the  iafteals  ; and  the  body  becomes  greatly  emaciated 
in  a fmall  time. 

I have  feen  feveral  patients  in  this  difeafe,  of  which  the  fol- 
lowing are  the  circumftances.  1.  They  were  men  about  fifty 
years  of  age;  and  had  lived  freely  in  refpedl  to  fermented  li- 
quors. 2.  They  loft  their  appetite  to  animal  food.  3.  They 
became  fuddenly  emaciated  to  a great  degree.  4.  Their  fkins 
were  dry  and  rough.  5.  Thev  coughed  and  expectorated  with- 
difficulty  a vifcid  phlegm.  6.  The  membrane  of  the  tongue  was 
dry  and  red,  and  liable  to  become  ulcerous. 

The  inability  to  digeft  animal  food,  and  the  confcquent  dif- 
tafte  to  it,  generally  precedes  the  dropfy,  and  other  difeafes, 
which  originate  from  lpirituous  potation.  I fuppofe,  when  the 
ftomach  becomes  inirri table,  that  there  is  at  the  fame  time  a de- 
ficiency ofgaftric  acid ; hence  milk feldom  agrees  withthefe  pa- 
tients, unlefs  it  be  previoufly  curdled,  as  they  have  not  fufficient 
gaftric  acid  to  curdle  it;  and  hence  vegetable  food,  which  is  it- 
felf  acefcent,  will  agree  with  their  ftomachs  longer  than  animal 
food,  which  requires  more  of  the  gaftric  acid  for  its  digeition. 

In  this  difeafe  the  {kin  is  dry  from  the  ir.creafed  abforption 
of  the  cutaneous  lymphatics,  the  fat  is  abforbed  from  the  in- 
creafed  abforption  of  the  cellular  lymphatics,  the  mucus  of 
the  lungs  is  too  vifcid  to  be  eafily  fpit  up  by  the  increafed  ab- 
forption of  the  thinner  parts  of  it,  the  membrana  fneideriana 
becomes  dry,  covered  with  hardened  mucus,  and  at  length  be- 
comes inflamed  and  full  of  apthae,  and  either  thefe  Houghs,  or/ 
pulmonary  ulcers,  terminate  the  fcene. 

II.  The  immediate  caufe  of  dropfy  is  the  paralyfis  of  fome 
other  branches  of  the  abforbent  fyftem,  which  are  called  lym- 
phatics, and  which  open  into  the  larger  cavities  of  the  body,  or 
into  the  cells  of  the  cellular  membrane  ; whence  thofe  cavities  or 
ceils  become  diftended  with  the  fluid,  which  is  hourly  fecreted 
into  them  for  the  purpofe  of  lubricating  their  furtaces,  as  is 
more  fully  explained  in  No.  5.  of  the  next  Sedlion. 

As  thofe  lymphatic  veflels  conlift  generally  of  a long  neck  or 
mouth,  which  drinks  up  its  appropiated  fluid,  and  of  a conglo- 
bate gland,  in  which  this  fluid  undergoes  fome  change,  it  hap- 
pens, that  fometimes  the  mouth  of  the  lymphatic,  and  fometimes 
tiie  belly  or  glandular  part  of  it,  becomes  totally  or  partially 
paralytic.  In  the  former  cafe,  where  the  mouths  of  the  cuta- 
neous lymphatics  become  torpid  or  quiefcent,  the  fluid  fecreted 
on  the  {kin  ceafes  to  be  abforbed,  and  erodes  the  {kin  by  its  fa- 
line  acrimony,  and  produces  eruptions,  termed  herpes,  the 
diicharge  from  which  is  as  fait  as  the  tears,  which  are  fecret- 


Sect.  XXVIII.  2.  ABSORBENT  SYSTEM. 


221 


ed  too  faft  to  be  reabforbed,  as  in  grief,  or  when  the  pundfa 
lacrymalia  are  obftrudied,  and  which,  running  down  the  cheek, 
redden  and  inflame  the  fkin. 

When  the  mouths  of  the  lymphatics,  which  open  on  the 
mucus  membrane  of  the  noftrils,  become  torpid,  as  on  walk- 
ing into  the  air  in  a frofty  morning,  the  mucus,  which  con- 
tinues to  be  fecreted,  has  not  its  aqueous  and  faline  part  reab- 
forbed, which,  running  over  the  upper  lip,  inflames  it,  and  has 
a fait  tafte,  if  it  falls  on  the  tongue. 

When  the  belly  or  glandular  part  of  thefe  lymphatics  be- 
comes torpid,  the  fluid  abforbed  by  its  mouth  ftagnates,  and 
forms  a tumour  in  the  gland.  This  difeafe  is  called  the  fcro- 
phula.  If  thefe  glands  fuppurate  externally,  they  gradually 
heal,  as  thofe  of  the  neck ; if  they  fuppurate  without  an  open- 
ing on  the  external  habit,  as  the  mefenteric  glands,  a hectic 
fever  enfues,  which  deftroys  the  patient;  if  they  fuppurate  in 
the  lungs,  a pulmonary  confumption  enfues,  which  is  believed 
thus  to  differ  from  that  defcribed  in  the  preceding  Section,  in 
refpedt  to  its  feat  or  proximate  caufe. 

It  is  remarkable,  that  matter,  produced  by  fuppuration,  will 
lie  concealed  in  the  body  many  weeks,  or  even  months,  with- 
out producing  hedtic  fever ; but  as  foon  as  the  wound  is  open- 
ed, fo  as  to  admit  air  to  the  furface  of  the  ulcer,  a hectic  fe- 
wer fupervenes,  even  in  -very  few  hours,  which  is  probably 
.owing  to  the  azotic  part  of  the  atmofphere  rather  than  to  the 
cxygene ; becaufe  thofe  medicines  which  contain  much  oxy- 
gene,  as  the  calces  or  oxydes  of  metals,  externally  applied, 
greatly  contribute  to  heal  ulcers : of  thefe  are  the  folutions  of 
lead  and  mercury,  and  copper  in  acids,  or  their  precipitates. 

Hence,  when  ulcers  are  to  be  healed  by  the  firft  intention,  as 
it  is  called,  it  is  necefla-ry  carefully  to  exclude  the  air  from 
them.  Hence  wTe  have  one  caufe,  which  prevents  pulmonary- 
ulcers  from  healing,  which  is  their  being  perpetually  expofed 
to  the  air. 

Both  the  dark-eyed  patients,  which  are  affedted  with  pul- 
monary ulcers  from  deficient  venous  abforption,  as  defcribed 
in  Sedf.  XXVII.  2.  and  the  light-eyed  patients  from  deficient 
lymphatic  abforption,  which  we  are  now  treating  of,  have 
generally  large  apertures  of  the  iris:  thefe  large  pupils  of  the 
eyes  are  a common  mark  of  want  of  irritability ; and  it  gene- 
rally happens,  that  an  increafe  of  fenfibility,  that  is,  of  motions, 
in  confequence  of  fenfation,  attends  thefe  conftitutions.  See 
Sedf.  XXXI.  2.  Whence  inflammations  may  occur  in  thefe 
irom  ftagnated  fluids  more  frequently  than  in  thofe  conftitu- 
tions which  poiTefs  mot  e irritability  and  lefs  fenfibility. 


Great 


222  RETROGRADE  ABSORBENTS.  Sect.XXTX. 

Great  expectations,  in  refpeit  to  the  cure  of  confumption;, 
as  well  as  of  many  other  dileafes,  are  produced  by  the  verv 
ingenious  exertions  of  Dr.  Beddoes;  who  has  eftablifheq 
an  apparatus  for  breathing  various  mixtures  of  airs  or  gaffes, 
at  the  hot-wells  near  Briftol,  which  well  deferves  the  attention 
of  the  public. 

Dr.  Beddoes  very  ingenioufly  concludes,  from  the  florid 
colour  of  the  blood  of  coniumptive  patients,  that  it  abounds 
in  oxygene;  and  that  the  rednefs  of  their  tongues,  and  lips, 
and  the  fine  blufh  of  their  cheeks  Anew  the  prelence  of  tire 
fame  princ  iple,  like  fiefh  reddened  by  nitre.  And  adds,  that 
the  circamftance  of  the  confumptions  of  pregnant  women  be- 
ing flopped  in  their  progrels  during  pregnancy,  at  which  time 
their  blood  may  be  fuppofed  to  be  m pare  deprived  of  its  oxy- 
gene,  by  oxygenating  the  blood  of  the  foetus,  is  a forcible 
argument  in  favour  of  this  theory ; which  mull  foon  be  con- 
firmed or  confuted  by  his  experiments.  See  EBay  on  Scurvy, 
Conlumption,  ccc.  by  Dr.  Beddoes.  Murray.  London.  Alio 
Letter  to  Dr.  Darwin,  bv  the  fame.  Murrav.  London. 


SECT.  XXIX. 

ON  THE  RETROGRADE  MOTIONS  OF  THE  ABSOR- 
BENT SYSTEM. 

I.  Account  of  the  ahf orient  fyfiem.  II.  The  valves  of  the 
alforbent  vrffels  may  fuff er  their  f uids  to  regurgitate  in 
fome  difeajes.  III.  Communication  from  the  alimentary 
canal  to  the  bladder  by  means  of  the  abforbent  veffels. 
IV.  The  phenomena  of  diabetes  explained.  V.  i.  The 
phenomena  of  dropfes  explained.  2.  Cafes  of  the  ufe 
of  foxglove.  VI.  Of  cold  fiveats.  VII.  Tranf.ations 
of  matter , of  chyle,  of  milk,  of  urine.  Operations  of  purg- 
ing drugs  applied  externally.  VII  I.  Circumfanccs  hi 
•which  the  finds,  that  are  effufed  by  the  retrograde  mo- 
tions of  the  abforbent  veffels,  are  d'lfiinguij/ied.  IX. 
Retrograde  motions  of  vegetable  juices.  X.  Objeflions 
an  fiver ed.  XI.  The  caujes  -which  induce  the  retrograde 
motions  of  animal  veffels,  and  the  medicines  by  -which  the 
natural  motions  are  refored. 

N.  B.  The  following  Se  Elion  is  a translation  of  a part  of  a 
Latin  thefis,  written  by  the  late  Mr.  Charles  Darwin, 
which  was  printed  with  his  pr  'vze-differtation  on  a crite- 
rion between  matter  and  mucus,  in  17S0.  Sold  by  Cadet! , 
London . 

I.  Account 


Sect.XXIX.  i.  RETROGRADE  ABSORBENTS.  223 

I.  Account  af  the  abforhent  fyftem. 

1.  THE  absorbent  fyftem  of  veffels  in  animal  bodies  con- 
fifts  of  feveral  branches,  differing  in  refpedb  to  their  fituations, 
and  to  the  fluids  which  they  abforb. 

The  inteftinal  abforbents  open  their  mouths  on  the  internal 
forfaces  of  the  ihteftines , their  office  is  to  drink  up  the  chyle 
and  the  other  fluids  from  the  alimentary  canal ; and  they  are 
termed  la  Heals,  to  diftinguifh  them  from  the  other  abforbent 
veffels,  which  have  been  termed  lymphatics. 

Thofe,  whole  mouths  are  difperied  on  the  external  lkin, 
imbibe  a great  quantity  of  water  from  the  atmoiphere,  and  a 
part  of  the  perfpirable  matter,  which  does  not  evaporate,  and 
are  termed  cutaneous  abforbents. 

Thofe,  which  arife  from  the  internal  furface  of  the  bron- 
chia, and  which  imbibe  moifture  from  the  atmofphere,  and  a 
part  of  the  bronchial  mucus,  are  called  pulmonary  ablorbents. 

Thofe,  which  open  their  innumerable  mouths  into  the  cells 
of  the  whole  cellular  membrane,  and  whofe  ufe  is  to  take 
up  the  fluid,  which  is  poured  into  thofe  cells,  after  it  has 
done  its  office  there,  may  be  called  cellular  abforbents. 

Thofe,  which  arife  from  die  internal  furtaces  of  the  mem- 
branes, which  line  the  larger  cavities  of  the  body,  as  the  tho- 
rax, abdomen,  fcrotum,  pericardium,  take  up  the  mucus  pour- 
ed into  thofe  cavities ; and  are  diftinguifhed  by  the  names  of 
their  refpedtive  cavities. 

Whilft  thofe,  which  arife  from  the  internal  furfaces  of  the 
urinary  bladder,  gall-bladder,  falivary  dudfs,  or  other  recep- 
tacles of  fecreted  fluids,  may  take  their  names  from  thofe  flu- 
ids, the  thinner  parts  of  which  it  is  their  office  to  abforb;  as 
urinary,  bilious,  or  falivary  abforbents. 

2.  Many  of  thefe  abforbent  veffels,  both  laHeals  and  lym- 
phatics,' like  fome  of  the  veins,  are  replete  with  valves ; which 
feem  defigned  to  affift  the  progrefs  of  their  fluids,  or  at  leaf!: 
to  prevent  their  regurgitation,  where  they  are  fubjedfed  to  the 
intermitted  preffure  or  the  mufcular,  or  arterial  addons  in 
their  neighbourhood. 

Thefe  valves  do  not,  however,  appear  to  be  neceffary  to  all 
the  abforbents,  any  more  than  to  all  the  veins ; fince  they  are 
hot  found  to  exift  in  the  abforbent  fyftem  of  fifh,  according 
to  the  difcoveries  of  the  ingenious  and  much  lamented  Mr. 
Hewfon.  Philcf.  Tranf.  v.  59.  Enquiries  into  the  Lymph. 
Syft.  p.  94. 

3.  Thefe  abforbent  veffels  are  alfo  furnifhed  with  glands, 
which  are  called  conglobate  glands ; whofe  ufe  is  not  at  pre- 
lent 


az4  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  2. 

fent  fufficiently  inveftigated ; but  it  is  probable  that  they  re- 
ferable the  conglomerate  glands,  both  in  ftruclure  and  in  ufe. 
except  that  their  abforbent  mouths  are,  for  die  conveniency  of 
lituation,  placed  at  a greater  diftance  from  the  body  of  the 
gland.  The  conglomerate  glands  open  their  mouths  immedi- 
ately into  the  fanguiferous  veffels  which  bring  the  blood,  from 
whence  diey  abforb  their  lefpeddive  fluids,  quite  up  to  the  gland: 
but  thefe  conglobate  glands  coliedt  their  adapted  fluids  from  ve- 
ry diftant  membranes,  or  cyfts,  by  means  of  mouths  fumifhed 
■with  long  necks  for  this  purpofe,  and  which  are  called  lacreuls, 
or  lymphatics. 

4.  The  fluids,  thus  collected  from  various  parts  of  the  body, 
pafs  by  means  of  the  thoracic  du£f  into  the  left  fubclavian  near 
the  jugular  vein ; except,  indeed,  that  thofe  colletfled  from  the 
right  lide  of  the  head  and  neck,  and  from  the  right  arm,  are  car- 
ried into  the  right  fubclavian  vein:  andfometimes  even  the  lym- 
phatics from  the  right  fide  of  the  lungs  are  inferted  into  the  right 
iubclavian  vein;  whilft  thofe  of  the  left  fide  of  the  head  open 
but  juft  into  the  fummit  of  the  thoracic  dudt. 

5.  In  the  abforbent  fyftem  there  are  many  anaftomofes  of  the 
veffels,  which  feem  of  great  confequence  to  the  prefervation  of 
health.  Thefe  anaftomofes  are  difeovered  by  diftedlion  robe 
very  frequent  between  the  inteftmal  and  urinary  lymphatics,  as 
mentioned  by  Mr.  Hewfon,  (Phil.  Tranf.  v.  58.) 

6.  Nor  do  all  the  inteftinal  abforbents  feem  to  terminate  in 
the  thoracic  du£t,  as  appears  from  feme  curious  experiments  of 
D.  Monro,  who  gave  madder  to  fome  animals,  having  previouf- 
ly  put  a ligature  on  die  thoracic  du£I,  and  found  their  bones, 
and  the  ferum  of  their  blood,  coloured  red. 

II.  The  Valves  of  the  Abforb  eni  SjJlcm  may  [ujfer  their 
Fluids  to  regurgitate  in  fome  JDifeafes. 

1.  The  many  valves,  which  occur  in  the  progrefs  of  the  lym- 
phatics and  laddeal  veffels,  would  feem  infuperable  obftacies  to 
the  regurgitation  of  their  contents.  But  as  thefe  valves  are  plac- 
ed in  veffels  which  are  indued  with  life,  and  are  themfelves  en- 
dued with  life  alfo,  and  are  very  irritable  into  thofe  natural  mo- 
rions which  abforb,  or  propel  the  fluids  they  contain  ; it  is  pofftble, 
in  fome  difeafes,  where  thefe  valves  or  veffels  are  itimulated  into 
unnatural  exertions,  or  ate  become  paralytic,  that  during  the 
diaftoleof  the  parrot  theveffel  to  which  the  valve  is  attached,  die 
valve  mav  not  fo  completely  clofe  as  to  prevent  the  relapfe  of  the 
lymph  or  chyle.  This  is  rendered  more  probable,  by  the  experi- 
ments of  injecting  mercury,  or  water,  or  luet,  or  by  blowing  air 
down  thefe  veffels ; ali  which  pafs  the  valves  very  eaftly,  contrary 

to 


Sect.  XXIX.  2.  RETROGRADE  ABSORBENTS.  225 


to  the  natural  courfe  of  their  fluids,  when  the  vefiels  are  thus 
a little  forcibly  dilated,  as  mentioned  by  Dr.  Haller.  Elern,. 
Phyflol.  T.  iii.  f.  4. 

“ The  valves  of  the  thoracic  dud  are  few;  fome  afiert  they 
are  not  more  than  twelve,  and  that  they  do  not  very  accurately 
perform  their  office,  as  they  do  not  clofethe  whole  area  of  the 
du£f,  and  thence  may  permit  chyle  to  repafs  them  downwards, 
hr  living  animals,  however,  though  not  always,  yet  more  fre- 
quently than  hr  the  dead,  they  prevent  the  chyle  from  returning. 
The  principal  of  thele  valves  is  that  which  prefides  over  the  in- 
fection of  the  thoracicdudl,  into  the  fubclavian  vein  : manybave 
believed  this  alfo  to  perform  the  office  of  a valve,  both  to  admit 
tire  chyle  into  the  vein,  and  to  preclude  the  blood  from  entering 
the  dud:  ; but  in  my  opinion  it  is  fcarcely  fufficient  for  this  pur- 
pofe.”  Haller,  Elem.  Phyf.  T.  vii.  p.  226. 

2.  The  mouths  of  the  lymphatics  feemto  admit  water  to  pafs 
through  them  after  death,  the  inverted  way,  eaf'ier  than  the 
natural  one  ; fince  an  inverted  bladder  readily  lets,  out  the  wa- 
ter with  which  it  is  filled  whence  It  may  be  inferred,  that  there 
is  no  obftacle  at  the  mouths  of  thefe  vefiels  to  prevent  the  re- 
gurgitation of  their  contained  fluids. 

I was  induced  to  repeat  this  experiment;  and  having  accu- 
rately tied  the  ureters  and  neck  of  a freflr  ox’s  bladder,  I made 
an  opening  at  the  fundus  of  it;  and  then,  having  turned  it  in- 
fide  outwards,  filled  it  half  full  with  water,  and  was  furprrfed 
to  fee  it  empty  itfelf  fo  haftily.  I thought  the  experiment  more 
appefite  to  my  purpofe,  by  fufpending  the  bladder  with  its  neck 
downwards,  as  the  lymphatics  are  chiefly  Ipread  upon  this  part 
of  it;  as  fhewn  by  Dr,  Watfcn,  Philoi.  Tranf.  v.  59,  p.  392. 

3.  In  fome  difeafes,  as  in  the  diabetes  and  fcrophuia,  it  is 


probable  the  valves  themfelves  are  difeafed,  and  are  thence  in- 
capable of  preventing  the  return  of  the  fluids  they  flhould  iup- 
port.  Thus  the  valves  of  the  aorta  itfelf  have  frequently  been, 
found  fchirrous,  according  to  the  difiedioris  of  Monk  Lieu- 
taud,  and  have  given  rife  to  an  interrupted  pulfe,  and  labori- 
ous palpitations,  byfuffiering  a return  of  part  of  the  blood  into 
the  heart.  Nor  are  any  parts  of  the  body  fo  liable  to  fchir- 
rofity,  as  the  lymphatic  glands  and  vefiels,  infomuch,  that  their 
fchirrofities  have  acquit  ed  a diftindt  name,  and  been,  termed 
fchrophula. 

4.  There  are  valves  in  other  parts  of  the  body,  analogous 
to  thofe  of  the  abforbent  fyftem,  and  which  are  liable,  when 
difeafed,  to  regurgitate  their  contents  : thus  the  upper  and 
lower  orifices  of  the  ftomach  are  doled  by  valves,  which, 
when  too  great  quantities  of  warm  water  have  been  drank, 

with. 


226  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  2. 

with  a defign  to  promote  vomiting,  have  fometimes  refilled  the 
utmoft  efforts  of  the  abdominal  mufeles  and  diaphragm : yet, 
at  other  times,  the  upper  valve,  or  cardia,  eafdy  permits  the 
. evacuation  of  the  contents  of  the  ftomach,  whilft  the  infe- 
rior valve,  or  pylorus,  permits  the  bile,  and  other  contents  of 
the  duodenum,  to  regurgitate  into  the  ftomach. 

5.  The  valve  of  the  colon  is  well  adapted  to  prevent  the  retro- 
grade motion  of  the  excrements ; yet,  as  this  valve  is  poffeffed 
of  a living  power,  in  the  iliac  paffion,  either  from  fpafm,  or 
other  unnatural  exertions,  it  keeps  itfelf  open,  and  either  buf- 
fers or  promotes  the  retrograde  movements  of  die  contents  of 
the  inteiti ties  below;  as  in  ruminating  animals,  the  mouth  of 
the  firft  ftomach  feetns  to  be  fo  comtruCted,  as  to  facilitate  or 
affift  the  regurgitation  of  the  food ; the  rings  of  the  cefopha- 
gus  afterwards  contracting  themfelves  in  inverted  order.  De 
Elaen,  by  means  of  a fyringe,  forced  fo  much  water  into  the 
reCtum  inteftinum  of  a dog,  that  he  vomited  it  in  a full  dream 
from  his  mouth  ; and  in  the  iliac  paffion  above-mentioned, 
excrements  and  clyfler  are  often  evacuated  by  the  mouth. 
See  SeCtion  XXV.  15. 

6.  The  punCta  lacrymalia,  with  the  lacrymal  back  and  nafal 
duCt,  compote  a complete  gland,  and  much  refemble  die  intef- 
tinal  canal;  the  punCta  lacrymalia  are  abi'orbent  mouths,  that 
take  up  the  tears  from  the  eye,  when  they  have  done  their  of- 
fice there,  and  convey  them  into  the  noftrils ; but  when  the 
nafal  duCt  is  obftruCted,  and  the  lacrvmal  lack  diltended  with 
its  fluid,  on  preffure  with  the  finger,  the  mouths  of  this  gland, 
(punCta  lacrymalia)  will  readily  difgorge  the  fluid  they  had 
previoufly  abforbed  back  into  the  eye. 

7.  As  the  capillary  veffels  receive  blood  from  die  arteries, 
and  feparating  the  mucus,  or  perfpirable  mat  er  from  it,  con- 
vey the  remainder  back  by  the  veins ; thele  capillary  veffels  are 
a let  of  glands,  in  every  reipeCt  fimilar  to  the  lecretory  vef- 
fels of  the  liver,  or  other  large  congeries  of  glands.  The  be- 
ginnings of  thefe  capillary  veffels  have  frequent  anaftomofes 
into  each  other,  in  which  circumftance  thev  are  relembled  bv 
the  laCteals ; and,  like  the  mouths  or  beginnings  of  odier 
glands,  they  are  a bet  of  abforbent  veffels,  which  drink  up  the 
blood  which  is  brought  to  them  by  the  arteries,  as  die  chyle  is 
drank  upby  the  laCteals : for  the  circulation  of  the  blood  through 
the  capillaries  is  proved  to  be  independent  of  arterial  impulie; 
lince,  in  theblufli  of  fliame,  and  in  partial  inflammations,  their 
aCtion  is  increafed,  without  any  increaie  of  die  motion  of  the 
heart. 

8.  Yet  not  only  the  mouths,  or  beginnings  of  diefe  anafto- 

mofing 


Sect.  XXIX.  3.  RETROGRADE  ABSORBENTS.  227 

moftng  capillaries  are  frequently  feen,  by  microfcopes,  to  re- 
gurgitate fome  particles  of  blood,  during  the  ftruggles  of  the 
animal ; but  retrograde  motion  of  th£  blood,  in  the  veins  of 
thole  animals,  from  the  very  heart  to  the  extremity  of  the  limbs, 
is  obfervable,  by  intervals,  during  the  di  (Irenes  of  tire  dving 
creature.  Haller,  Elern.  Phyfiol.  T.  i.  p.  216.  Now,  as  the 
veins  have  perhaps  all  of  them  a valve,  fomewhere  between 
their  extremities  and  the  heart,  here  is  ocular  demonftration  of 
the  fluids  in  this  difeafed  condition  of  the  animal,  repairing 
through  venous  valves  : and  it  is  hence  highly  probable,  from 
the  ftiidleft  analogy,  that  if  the  courie  of  the  fluids,  in  the  lym- 
phatic veffeis,  couid  be  fubjecled  to  microiccpic  obiervation, 
they  would  alfo,  in  the  difeafed  llate  of  the  animal,  be  feen  to 
repafs  the  valves,  and  the  mouths  of  thole  veffeis  which  had  pre- 
vioufly  ablorbed  them,  or  promoted  their  progreffion. 

III.  Communication  from  the  Alimentary  Canal  to  the  Blad- 
der, by  means  of  the  A'oforbcnt  V effAs. 

Many  medical  philofophers,  both  ancient  and  modern,  have 
fufpedled  that  there  was  a nearer  communication  between  the 
ftomach  and  the  urinary  bladder  than  that  of  the  circulation  : 
they  were  led  into  this  opinion  from  the  great  expedition  with 
which  cold  water,  when  drank  to  excels,  paffes  cff  by  the 
bladder:  and  from  the- fnnilarity  of  the  urine,  when  produced 
in  this  hafty  manner,  with  the  material  that  was  drank. 

The  former  of  thefe  circumftances  happens  perpetually  to 
thofe  who  drink  abundance  of  cold  water  when  they  are  much 
heated  by  exerciit^  and  to  many  at  the  beginning  of  intoxication. 

Of  the  latter  many  inftances  are  recorded  by  Etmuller,  T. 
xi.  p.  7 16.  where  fimple.  water,  wine,  and  wine  with  lugar,  and 
emulfions,  were  returned  by  urine  unchanged. 

There  are  other  experiments,  that  feem  to  demonftrate'the 
exigence  of  another  paffage  to  the  bladder  befrdes  that  chrough 
the  kidneys.  Thus  Dr.  Kratzenftein  put  ligatures  on  the  ure- 
ters of  a dog,  and  then  emptied  the  bladder  by  a catheter;  yet 
in  a little  time  the  dog  drank  greedily,  and  made  a quantity  of 
water.  (Difputat.  Morbor.  Halleri.  T.  iv.  p.  63:)  A fimi- 
iar  experiment  is  related  in  the  Philofophical  Tranfadtions, 
with  the  fame  event.  (No.  65,  67,  for  the  year  1670.) 

Add  to  this,  that  in  fome  morbid  cafes  the  urine  has  continu- 
ed to  pafs,  after  the  fupuration  cr  total  deftrudfion  of  the  kid- 
neys ; of  which  many  inftances  are  referred  to  in  the  Elem, 
Phyfiol.  T.  vii.  p.  379,  of  Dr.  Haller. 

From  all  which  it  muft  be  concluded,  that  fome  fluids  have 
palled  from  the  ftomach,  or  abdomen,  without  having  gone 

H h through 


228  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  3. 

through  the  fanguiferous  circulation  : and  as  the  bladder  is  flip- 
plied  with  many  lymphatics,  asdefcribed  by  Dr.  Watfon,  in  the 
Philof.  Tranf.  v.  59.  p.  392.  and  as  110  other  vefiels  open 
into  it  befides  thefe  and  the  ureters,  it  feems  evident,  that  the 
unnatural  urine,  produced  as  above  defcribed,  when  the  ureters 
were  tied,  or  the  kidneys  obliterated,  was  carried  into  the  blad- 
der by  the  retrograde  motions  of  the  urinary  branch  of  the 
lymphatic  fyftera. 

Tire  more  certainly  to  afcertain  the  exifter.ce  of  another 
communication  between  the  ftomach  and  bladder,  befides  that 
of  the  circulation,  the  following  experiment  was  made,  to 
which  I rauft  beg  your  patient  attention:  A friend  of  mine 
(June  14,  1772,)  on  drinking  repeatedly  of  cold  fmall  punch, 
till  he  began  to  be  intoxicated,  made  a quantity  of  colourleA 
urine.  He  then  drank  about  two  drams  of  nitre,  diffolved  in 
fome  of  the  punch,  and  eat  about  twenty  ftalks  of  boiled  afpa- 
ragus : on  continuing  to  drink  more  of  the  punch,  the  next  urine 
that  he  made  was  quite  clear,  and  without  lmell ; but  in  a little 
time  another  quantity  was  made,  which  was  not  quite  fo  colour- 
lefs,  and  had  a ftrong  fmeli  of  the  afparagus : he  then  loft  about 
four  ounces  of  blood  from  the  arm- 

The  fmeli  of  the  afpa-ragus  was  not  at  all  perceptible  in  the 
blood,  neither  when  frefh  taken,  nor  the  next  morning,  as  my- 
felt  and  two  others  accurately  attended  to ; yet  this  fmeli  was 
ftrongly  perceived  in  the  urine  which  was  made  juft  before 
the  blood  was  taken  from  his  arm. 

Some  bibulous  paper,  moiftened  in  the  ferum  of  this  blood, 
and  fuffered  to  dry,  fhewed  no  ligns  of  nitre  by  its  manner  of 
burning.  But  fome  of  the  fame  paper,  moiftened  in  the  urine, 
and  dried,  on  being  ignited,  evidently  fhewed  the  prefence  of 
nitre.  This  blood  and  the  urine  flood  iome  days  expofed  to 
the  fun  in  the  open  air,  till  they  were  evaporated  to  about  a 
fourth  of  their  original  quantity,  and  began  to  ftink ; the  paper, 
which  was  then  moiftened  with  the  concentrated  urine,  Tew- 
ed the  prefence  of  much  nitre  by  its  manner  of  burning  ; whilft 
that  moiftened  with  the  blood  fhewed  no  fuch  appearance  at  all. 

Hence  it  appears,  that  certain  fluids,  at  the  beginning  of  in- 
toxication, find  another  paffage  to  the  bladder  befides  the  long 
courfe  of  tiie  arterial  circulation;  and  as  the  inteftinal  abior- 
bents  are  joined  with  the  urinary  lymphatics  by  frequent  anaf- 
tomofes,  as  Hewfpn  has  demonftrated  ; and  as  there  is  no  other 
road,  we  may  ju fitly  conclude,  that  thefe  fluids  pais  into  the 
bladder  by  the  urinary  branch  of  the  lymphatics,  which  has  its 
motions  inverted  during  the  diieafed  ftate  of  the  animal. 

A gentleman,  who  had  been  iome  weeks  atiedfed  with  jaun- 
dice* 


Sect.  XXIX.  4.  RETROGRADE  ABSORBENTS.  229 

dice,  and  whofe  urine  was,  in  confequence,  of  a very  deep  yellow, 
took  i'ome  cold  final  1 punch,  in  which  was  diffolved  about  a 
dram  of  nitre;  he  then  took  repeated  draughts  of  the  punch, 
•and  kept  himfelf  in  a cool  room,  till  on  the  approach  of  flight 
intoxication  he  made  a large  quantity  of  water ; this  water  had 
•a  flight  yellow  tinge,  as  might  be  expected  from  a fmall  admix- 
ture of  bile  fecreted  from  the  kidneys ; but  if  the  whole  of  it 
had  palled  through  the  fanguiferous  veffels,  which  were  now 
replete  with  bile  (his  whole  Ikin  being  as  yellow  as  gold)  would 
not  this  urine  alfo,  as  well  as  that  he  had  made  for  weeks  be- 
fore, have  been  of  a deep  yellow  ? Paper  dipped  in  this  water, 
and  dryed,  and  ignited,  fhewed  evident  marks  of  the  prefence  of 
nitre,  when  the  flame  was  blown  out. 

JV.  The  Phenomena  of  the  Diabetes  explained , and  of  fame 
Diarrhoeas. 

The  phenomena  of  many  difeafes  are  only  explicable  from 
rthe  retrograde  motions  of  fome  of  the  branches  of  the  lympha- 
tic fyftem  ; as  the  great  and  immediate  flow  of  pale  urine  in  the 
Beginning  of  drunkennefs;  in  hyftericparoxyfms  ; from  being 
.expofed  to  cold  air,  or  to  the  influence  of  fear  or  anxiety. 

Before  we  endeavour  to  illuftrate  this  dodtrine,  by  defer ibing 
the  phenomena  of  thefe  difeafes,  we  mud  premife  one  circunt- 
flance ; that  all  the  branches  of  the  lymphatic  fyftem  have  a 
certain  fympathy  with  each  other,  infomuch,  that  when  one 
branch  is  {Emulated  into  unufual  kinds  or  quantities  of  motion, 
fome  other  branch  has  its  motions  either  increafed,  or  decreaf- 
ed,  or  inverted  at  the  fame  time.  This  kind  of  fympathy  can 
only  be  proved  by  the  concurrent  teftimony  of  numerous  faffs, 
which  will  be  related  in  the  courfe  of  the  work.  I {hall  only 
add  here,  that  it  is  probable,  that  this  fympathy  does  not  de- 
pend on  any  communication  of  nervous  filaments,  but  on  ha- 
bit, owing  to  the  various  branches  of  this  fyftem  having  fre- 
quently been  {Emulated  into  affion  at  the  fame  time. 

There  are  a thoufand  inftanegs  of  involuntary  motions  aflfo- 
ciated  in  this  manner;  as  in  the  aft  of  vomiting,  while  the 
motions  of  the  ftomach  and  cefophagus  are  inverted,  the  pulfa- 
tions  of  the  arterial  fyftem,  by  a certain  fympathy,  become 
weaker ; and  when  the  bowels  or  kidneys,  are  {Emulated  by 
poifon,  a ftone,  or  inflammation,  into  more  violent  adtion,  the 
ftomach  and  cefophagus,  by  fympathy,  invert  their  motions.  \ 

1.  When  any  one  drinks  a moderate  quantity  of  vinous  fpi- 
rit,  the  whole  fyftem  adts  with  more  energy  by  confent  with 
the  ftomach  and  inteftines,  as  is  feen  from  the  glow  on  the  {kin, 
and  die  inereafe  of  ftrength  and  activity ; but  when  a greater 

quantity 


230  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  n. 

quantity  of  this  inebriating  material  is  drank,  at  the  fame  time 
that  the  iaGeals  are  excited  into  greater  aftion  to  abforb  it,  it 
frequently  happens,  thatthe  urinary  branch  of  abforbents,  which 
is  connected  with  the  lacteals  by  many  anaftomofes,  inverts  its* 
motions,  and  a great  quantity  of  pale  unanimalized  urine  is 
difeharged.  By  this  wile  contrivance  too  much  of  an  unne- 
ceffary  fluid  is  prevented  from  entering  the  circulation.  This 
may  be  called  the  drunken  diabetes,  to  diftineuifh  it  from  the 
other  temporary  diabetes,  which  occur  in  hyfteric  dileafcs,  and 
from  continued  fear  oh  anxiety. 

2.  If  this  idle  ingurgitation  of  too  much  vinous  fpirit  be 
daily  pracf i fed,  the  urinary  branch  of  abforbents  at  length  chains 
an  habit  of  inverting  its  motions,  whenever  the  lacteals  are 
much  Simulated:  and  the  whole,  or  a great  part  of  the  chyle 
is  thus  daily  carried  to  the  bladder,  without  entering  the  circu- 
lation, and  the  body  becomes  emaciated.  This  is  one  kind  of 
chronic  diabetes,  and  may  be  diftinguifhed  from  the  others  bv 
thetafteand  appearance  of  the  urine;  which  is  iweet,  and  the 
colour  of  whey,  and  may  be  termed  the  chylilerous  diabetes. 

3.  Many  children  have  a fimilar  depofuion  of  chyle  in  their 
urine,  from  the  irritation  of  worms  in  their  inteflines,  which 
ftimuiating  the  mouths  of  the  lacteals  into  unnatural  adtion, 
the  urinary  branch  of  the  abforbents  becomes  inverted,  and 
carries  part  of  the  chyle  to  the  bladder  : part  of  the  chyle  aifo 
has  been  carried  to  the  iliac  and  lumber  glands,  of  which  in- 
ftances  are  recorded  by  Haller,  T.  vii.  225.  and  which  can  be 
explained  on  no  other  theory;  but  the  dilledtions  of  the  lym- 
phatic iyftem  of  the  human  body,  which  have  yet  been  puhii/h- 
ed,  are  not  fufficiently  extenfive  for  ourpurpofe;  yet  if  we 
may  teuton  from  comparative  anatomy,  this  translation  of  chyle 
to  the  bladder  is  much  ill uft rated  by  the  account  given  of  this 
fyftem  of  vefiels  in  a turtle,  by  Mr.  Hewfon,  who  obferved, 

“ That  the  ladteals  near  the  root  of  the  melentery  anaftomofe, 
fo  as  to  form  a net-work,  from  which  feveral  large  branches 
go  into  fome  confiderable  lymphatics  lying  near  the  (pine ; and 
which  can  be  traced  almoft  to  the  anus,  and  particularly  to  the 
kidneys.”  Philof.  Tranf.  v.  59.  p.  199. — Enquiries,  p.  “4. 

4.  At  the  fame  time  that  the  urinary  blanch  of  abforbents, 
in  the  beginning  of  diabetes,  is  excited  into  inverted  adticn, 
the  cellular  branch  is  excited  by  the  fympathy  above  mention- 
ed, into  more  energetic  aGion;  and  the  fat,  that  was  before 
depofited,  is  venbforbed  and  thrown  into  the  blood  vefiels,  whew 
it  floats,  and  was  miftaken  for  chyle,  till  the  late  experiments 
of  the  ingenious  Mr.  Hewfon  demonftrated  it  to  be  tar. 

This  appearance  of  what  was  miftaken  for  chyle  in  the  blond 
1 which 


Sect.  XXIX.  4.  RETROGRADE  ABSORBENTS.  231 

which  was  drawn  from  thefe  patients,  and  the  obftruded  liver, 
which  very  frequently  accompanies  this  diieale,  feems  to  have 
led  Dr.  Mead  to  fufped  the  diabetes  was  owing  to  a defect  of 
fanpuification ; and  that  the  fchirrofity  of  the  liver  was  the  ori- 
ginal caule  of  it : but  as  the  fchirrous  of  the  liver  is  moft  fre- 
quently owing  to  the  fame  caul'es  that  produce  the  diabetes 
and  dropfles,  namely,  the  grearuie  of  fermented  liquors,  there 
is  no  wonder  they  ihould  exift  together,  without  being  the  con- 
fequence  of  each  other. 

5.  If  the  cutaneous  branch  of  abforbents  gains  a habit 
of  being  excited  into  ftronger  adion,  and  imbibes  greater  quan- 
tities of  m oifture  from  the  atmofphere,  at  the  fame  time  that  the 
urinary  branch  has  its  motions  inverted,  another  kind  of  diabe- 
tes is  formed,  which  may  be  termed  the  aqueous  diabetes.  In 
this  diabetes  the  cutaneous  abforbents  frequently  imbibe  an 
amazing  quantity  of  atmofpheric  moiflure ; infomuch  that  there 
are  authentic  hiilories,  where  many  gallons  a day,  for  many 
weeks  together,  above  the  quantity  that  has  been  drank,  have 
'been  difcharged  by  urine. 

Dr.  Keil,  in  his  Medicina  Statica,  found  that  he  gained 
eighteen  ounces  from  the  moift  air  of  one  night ; and  Dr.  Per- 
cival  affirms,  that  one  of  his  hands  imbibed,  after  being  well 
chafed,  near  an  ounce  and  half  of  water,  in  a quarter  of  an 
hour.  (Tranfad.  of  the  College,  London,  vol.  ii.  p.  102.) 
Home’s  Medic.  Fads,  p.  a.  feci.  3. 

The  pale  urine  in  hyfterical  women,  or  which  is  produced 
bv  fear  or  anxiety,  is  a temporary  complaint  of  this  kind : and  it 
would  in  reality  be  the  fame  difeai'e,  it  it  was  confirmed  by  habit. 

6.  The  purging  ftools,  and  pale  urine,  occafioned  by  expos- 
ing the  naked  body  to  cold  air,  or  Sprinkling  it  with  cold  wa- 
ter, originate  from  a fimilar  caufe;  tor  the  mouths  of  the  cu- 
taneous lymphatics  being  fuddenly  expofed  to  cold,  become  tor- 
pid, and  cede,  or  nearly  ceafe  to  ad;  rvhilft,  by  the  fvmpathv 
above  defer  i.bed,  not  only  the  lymphatics  of  the  bladder  and 
inteflines  ceafe  alfo  to  abforb  the  more  aqueous  and  f aline  part 
of  the  fluids  fecreted  into  them  ; but  it  is  probable  that  thefe 
lymphatics  invert  their  motions,  and  return  the  fluids,  which 
were  previoufly  abforbed,  into  the  inteflines  and  bladder.  At 
the  very  inftant  that  the  body  is  expofed  naked  to  the  cold  air, 
an  unufuai  movement  is  felt  in  the  bowels  ; as  is  experienced 
by  boys  going  into  the  cold  bath:  this  could  not  occur  from  an 
obltrudion  ot  the  peripirable  matter,  llnce  there  is  not  time  for 
that  to  be  returned  to  the  bowels  by  the  courfe  of  the  circulation. 

There  is  alto  a chronic  aqueous  diarrhoea,  in  which  the  at- 
rnofpheric  moifture,  drank  up  by  the  cutaneous  and  pulmonary 

lymphatics. 


2 32.  RETROGRADE  ABSORBENTS.  Sect.  XXIX. 4. 

lymphatics,  is  poured  into  the  inteftines,  by  the  retrograde 
motions  of  the  lacteals,.  This  difeafe  is  moft  fimilar  to  the 
aqueous  diabetes,  and  is  frequently  exchanged  for  it : a diftinct 
inftance  of  this  is  recorded  by  Benningerus,  Cent.  v.  Obf.  98. 
in  which  an  aqueous  diarrhoea  fucceeded  an  aqueous  diabetes, 
and  deftroyed  the  patient.  There  is  a curious  example  of  this 
deferibed  by  Symplon  (De  Re  Medina} — “ A young  man 
(days  he)  was  feized  with  a fever,  upon  which  a diarrhcea  came 
on,  with  great  ftupor,  and  he  refufed  to  drink  any  thing,  though 
he  was  parched  up  with  exceflive  heat : the  better  to  fupply  him 
with  moifture,  I directed  his  feet  to  be  immerfed  in  cold  water  ; 
immediately  I obferved  a wonderful  decreafe  of  water  iu  the 
yefTel,  and  then  an  impetuous  ftream  of  a fluid,  fcarcely  co- 
loured, was  difeharged  by  ftool,  like  a cataract.” 

7.  There  is  another  kind  of  diarrhoea  which  has  been  called 
caeliaca  ; in  this  difeafe  the  chyle,  drank  up  by  the  lacteals  of 
the  fmall  inteftines,  is  probably  poured  into  the  large  inteftines 
by  the  retrograde  motions  of  their  lafiteals ; as  in  the  chylife- 
rous  diabetes,  the  chyle  is  poured  into  the  bladder  by  the  retro- 
grade motions  of  the  urinary  branch  of  a'bforbents. 

The  chyliferous  diabetes,  like  this  chyleferous  diarrhoea,  pro- 
duces fudden  atrophy;  fince  the  nourifhment,  which  ought  to 
fupply  the  hourly  wafte  of  the  body,  is  expelled  by  the  bladder, 
or  refilum : whilft  the  aqueous  diabetes,  and  the  aqueous  diarr- 
hoea produce  exceflive  third;  becaufe  the  moifture,  which 
is  obtained  from  the  atmofphere,  is  not  conveyed  to  the  thora- 
cic receptacle  as  it  ought  to  be,  but  to  the  bladder,  or  lower 
inteftines  ; whence  the  chyle,  blood,  and  whole  fyftem  of  glands 
are  robbed  of  their  proportion  of  humidity. 

8.  There  is  a third  i'pecies  of  diabetes,  iu  which  the  urine  is 
mucilaginous,  and  appears  ropy  in  pouring  it  from  one  veflel 
into  another ; and  will  fome  times  coagulate  over  rhe  fire. 
This  difeafe  appears  by  intervals,  and  ceafes  again,  and  feems 
to  be  occafioned  by  a previous  dropfy  in  fotne  part  of  the  bo- 
dy. When  fuch  a colledfion  is  reabforbed,  it  is  not  always 
returned  into  the  circulation ; but  the  fame  irritation  that  ftimu- 
lutes  one  lymphatic  branch  to  reablorb  the  depoiited  fluid,  in- 
verts the  urinary  branch,  and  pours  it  into  the  bladder.  Hence 
this  mucilaginous  diabetes  is  a cure,  or  the  confequeuce  of  a 
cure,  of  a worfe  difeafe,  rather  than  a difeafe  itfelf. 

Dr.  Cotunnius  gave  half  an  ounce  of  cream  of  tartar,  eve- 
ry morning,  to  a patient  who  had  the  anafarca ; and  he  voided 
a"  great  quantity  of  urine;  a part  of  which,  put  over  the  fire, 
coagulated,  on  the  evaporation  of  half  of  it,  lb  as  to  look  like 
the  white  of  an  egg.  De  Ilchiaue  Nerves. 


This 


Sect.  XXIX.  4.  RETROGRADE  ABSORBENTS.  233 

This  kind  of  diabetes  frequently  precedes  a drdpfy ; and  has 
this  remarkable  circumftance  attending  it.  that  it  generalfyhap- 
pens  in  the  night;  as  during  the  recumbent  (fate  of  the  body, 
the  fluid,  that  was  accumulated  in  the  cellular  membrane,  or  in 
the  lungs,  is  more  readily  abforbed,  as  it  is  lefs  impeded  by  its 
gravity.  I have  feen  more  than  one  inftartce  of  this  difeafe. 
Air.  D.  a man  in  the  decline  of  life,  who  had  long  accuftom- 
ed  himfeif  to  fpirituous  liquor,  had  {'welled  legs,  and  other  fymp- 
torns  of  approaching  anafarca ; about  once  in  a week,  or  ten 
days,  for  feveral  months,  he  was  feized,  on  going  to  bed,  with 
great  general  uneahnefs,  which  bis  attendants  relembled  to  an 
hyfteric  fit,  and  which  terminated  in  a great  difcharge  of  vi- 
fcid  urine;  his  legs  became  lei's  fwelied,  and  he  continued  in 
better  health  for  forne  days  afterwards.  I had  not  the  oppor- 
tunity to  try  if  this  urine  would  coagulate  over  the  fire,  when 
part  of  it  was  evaporated,  which  I imagine  would  he  the  cri- 
terion of  this  kind  of  diabetes,  as  the  mucilaginous  fluid  depo- 
flted  in  the  cells  and  cyfts  of  the  body,  which  have  no  commu- 
nication with  the  external  air,  feems  to  acquire,  by  ftagnation, 
this  property  of  coagulation  by  heat,  which  the  fecreted  mu- 
cus of  the  inteftines  and  bladder  do  not  appear  to  poffefs,  as  I 
have  fouixl  by  experiment ; and  if  any  one  fliould  fuppofe  this 
coagulable  urine  was  feparated  from  the  blood  by  the  kidneys, 
he  may  recoiled!:,  that  in  the  mod  inflammatory  difeafes,  in 
which  the  blood  is  mold  replete,  or  mod  ready  to  part  with  the 
coagulable  lymph,  none  of  this  appears  in  the  urine. 

9.  Different  kinds  of  diabetes  require  different  methods  of 
cure.  For  the  firft  kind,  or  chyliferous  diabetes,  after  clear- 
ing the  fcomach  and  inteftines,  by  ipecacuanha  and  rhubarb, 
to  evacuate  any  acid  material,  which  may  too  powerfully  fti- 
mulate  the  mouths  of  the  lacteals,  repeated  and  large  doles  of 
tinddure  of  cantharides  have  been  much  recommended.  The 
fpeciflc  ftimulus  of  this  medicine  on  the  neck  of  the  bladder,  is 
likely  to  excite  the  numerous  abforbent  vefiels,  which  are  fpread 
on  that  part,  into  ftronger  natural  addiOns,  and  by  that  means 
prevent  their  retrograde  ones ; till,  by  perflffing  in  the  ufe  of 
the  medicine,  their  natural  habits  of  motions  might  again  he 
eftablhhed.  Another  indication  of  cure  requires  filch  medi- 
cines as,  by  iining  the  inteftines  with  mucilaginous  iubftances, 
or  with  fuch  as  conftft  of  fmooth  particles,  or  which  chemi- 
cally deftroy  the  acrimony  of  their  contents,  may  prevent  the 
too  great  action  of  the  inteftinal  abforbents.  For  this  purpofe 
I have  found  the  earth  precipitated  from  a folution  of  alum,  by- 
means  of  fixed  alcali,  given  in  the  dofe  of  half  a dram  every  fix 
hours,  of  great  advantage,  with  a few  grains  of  rhubarb,  fo 
as  to  procure  a daily  evacuation. . 


The 


234  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  4. 

The  food  fhould  confift  of  materials  that  have  the  leaft  fti- 
mulus,  with  calcareous  water,  as  of  Briftol  and  Matlock  ; that 
the  mouths  of  the  ladfeals  may  be  as  little  ftimulated  as  is  ne- 
ceffary  tor  their  proper  abforption ; left  with  their  greater  ex- 
ertions fhould  be  connedted  by  fympathy  the  inverted  motions 
of  the  urinary  lymphatics. 

The  fame  method  may  be  employed,  with  equal  advantage, 
in  the  aqueous  diabetes,  fo  great  is  the  fympathy  between  :hc 
fkin  and  the  ftomach.  To  which,  however,  fome  application 
to  the  fkin  might  be  ufefully  added  ; as  rubbing  the  patient  ait 
over  with  oil,  to  prevent  the  too  great  action  ot  die  cutanea 
ous  abforbents.  I knew  an  experiment  of  this  kind  made  upon 
one  patient  with  apparent  advantage. 

The  mucilaginous  diabetes  will  require  the  fame  treatment, 
which  is  moft  efficacious  in  the  dropiy,  and  will  be  defcribed 
below.  I muft  add,  that  the  diet  and  medicines  above  mention- 
ed, are  ftrongly  recommended  by  various  authors,  as  by  Mor- 
gan, W illis,  Harris,  and  Efmuller ; but  more  hiftories  of  die 
fuccefsful  treatment  of  thefe  difeafes  are  wanting  to  lolly  after- 
tain  the  moft  efficacious  methods  of  cure. 

In  a letter  from  Mr.  Charles  Darwin,  dated  April  24,  1778, 
Edinburgh,  is  the  lubfequent  paffages:— - “ A man  who  long 
laboured  under  a diabetes  died  yefterday  in  the  clinical  ward. 
He  had  for  fome  time  drank  four,  and  puffed  twelve  pounds  cf 
fluid  daily  ; each  pound  of  urine  contained  an  ounce  of  iugar. 
He  took,  without  ccnliderable  reliet,  gum  kino,  ianguis  dra- 
conis  melted  with  alum,  tindfureof  cantharides,  ilinglais,  gum 
arable,  crabs  eyes,  fpirit  of  hartfhorn,  and  eat  ten  or  fifteen 
oyfters  thrice  a day.  Dr.  Home,  having  read  my  thefis,  bird 
him,  and  found  that  neither  the  frefh  blood  nor  the  fe,  urn  tailed 
lvveet.  His  body  was  opened  this  morning — -every  vifeus  ap- 
peared in  a found  and  natural  ftate,  except  that  the  leftkidnev 
had  a very  fmall  pelvis,  and  that  there  was  a conliderable  en- 
largement of  moft  of  the  mefenteric  lymphatic  glands.  1 in- 
tend to  infert  this  in  my  thchs,  as  it  coincides  with  the  ex- 
periment, where  fome  afparagus  was  eaten  at  the  beginning  of 
intoxication,  and  its  fmell  perceived  in  the  urine,  though  not 
in  the  blood.” 

The  following  cafe  of  chyliferous  diabetes  is  extracted  hom 
fome  letters  of  Mr.  Hughs,  to  whole  miremitted  care  die  in  - 
firmary at  Stafford  tor  many  years  was  much  indebted,  dated 
October  10,  1778. 

Richard  Davis,  aged  33,  a whitefmith  by  trade,  had  crank 
hard  by  intervals ; was  much  troubled  with  1 ’.vesting  ot  tu.> 
hands,  which  incommoded  him  in  his  occupation,  but  whit  h 

tea  led 


Sect.  XXIX.  4.  RETROGRADE  ABSORBENTS.  235 

ceafed  on  his  frequently  dipping  them  in  lime.  About  feven 
months  ago  he  began  to  make  large  quantities  of  water;  his 
legs  are  osdematous,  his  belly  tenfe,  and  he  complains  of  a ril- 
ing in  his  throat,  like  the  globus  hifterieus : he  eats  twice  as 
much  as  other  people,  drinks  about  fourteen  pints  of  fmall  beer 
a day,  betides  a pint  of  ale,  force  milk-porridge,  and  a bafon  of 
broth,  and  he  makes  about  eighteen  pints  of  water  a day. 

He  tried  alum,  dragon’s  blood,  fteel,  blue  vitriol,  and  can- 
tharides  in  large  quantities,  and  duly  repeated,  under  the  care 
of  Dr.  Underbill,  but  without  any  efFedt;  except  mat  on  the 
day  after  he  omitted  the  cantharides,  he  made  but  twelve  pints 
of  water;  but  on  the  next  day  this  good  effect  ceaied  again. 

November  21. — He  made  eighteen  pints  of  water,  and  he 
now,  at  Dr.  Darwin’s  requell,  took  a grain  of  opium  every 
four  hours,  and  five  grains  of  aloes  at  night ; and  had  a flannel 
fliirt  given  him. 

22.  — Made  llxteen  pints. 

23.  — Thirteen  pints:  drinks  lefs. 

24. — Increafed  the  opium  to  a grain  and  a quarter  every 
four  hours : he  made  twelve  pints. 

25. — Increafed  the  opium  to  a grain  and  half:  he  now 
makes  ten  pints,  and  drinks  eight  pints  in  a day. 

The  opium  was  gradually  increaied  during  dre  next  fort- 
night, till  he  took  three  grains  every  four  hours,  but  without 
any  further  diminution  of  his  water.  During  the  ufe  of  the 
opium  he  fweat  much  in  the  nights,  fo  as  to  have  large  drops 
ftand  on  his  face  and  all  over  him.  The  quantity  of  opium 
was  then  gradually  decreafed,  but  not  totally  omitted,  as  he 
continued  to  take  about  a grain  morning  and  evening. 

January  17. — He  makes  fourteen  pints  of  water  a day.  Dr. 
Underhill  now  dire  died  him  two  fcruples  of  common  rofin  tri- 
turated with  as  much  fugar,  every  fix  hours,  and  three  grains 
of  opium  every  night. 

19. — Makes  fifteen  pints  of  water:  fweats  at  night. 

21. — Makes  feventeen  pints  of  water;  has  twitchings  of  his 
limbs  in  a morning,  and  pains  of  his  legs:  he  now  takes  a 
dram  ot  rolin  for  a dofe,  and  continues  the  opium. 

23. — M ater  more  coloured,  and  reduced  to  llxteen  pints, 
and  he  thinks  has  a brackifh  tafle. 

26.  — Water  reduced  to  fourteen  pints. 

28. — Water  thirteen  pints:  he  continues  the  opium,  and 
takes  four  fcruples  ot  the  rofin  fora  dofe. 

February  1. — Water  twelve  pints. 

4- — W atei  eleven  pints ; twitchings  lefs  : takes  five  fcruples 
for  a dofe. 


li 


8. — Water 


236  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  4; 

8. — Water  ten  pints:  has  had  many  ftools. 

12. — Appetite  lels : purges  very  much. 

After  this  the  rofin  either  purged  him,  or  would  not  ftav  on 
his  ftomach;  and  he  gradually  relapied  nearly  to  his  former 
condition,  and  in  a few  months  funk  under  thedifeafe. 

Odtober  3. — Mr.  Hughes  evaporated  two  quarts  of  the  water, 
and  obtained  from  it  four  ounces  and  half  of  a hard  and  brit- 
tle faccharine  mafs,  like  treacle  which  had  been  fome  time 
boiled,  h our  ounces  of  blood,  which  he  took  from  his  arm 
with  defign  to  examine  it,  had  the  common  appearances,  ex- 
cept that  the  ferum  refembled  cheefe-whey ; and  that  on  the 
evidence  of  four  perions,  two  of  whom  did  not  know  what 
it  was  they  tafted,  the  ferum  had  a faltijh  tafle. 

From  hence  it  appears,  that  the  faccharine  matter,  with 
which  the  urine  of  thefe  patients  fo  much  abounds,  docs  not 
enter  the  blood  veffels  like  the  nitre  and  aiparagus  mentioned 
above ; but  that  the  procefs  of  digeftion  relemhles  the  proccis 
of  the  germination  of  vegetables,  or  of  making  barley  into 
malt ; as  the  vaft  quantity  of  fugar  found  in  the  urine  mud  be 
made  from  the  food  which  he  took  (which  was  double  that 
taken  by  others),  and  from  the  fourteen  pints  of  fmall  beer 
which  he  drank.  And,  fecondly,  as  the  ferum  of  the  blood 
was  not  fweet,  the  chyle  appears  to  have  been  conveyed  to  the 
bladder  without  entering  the  ciiculation  of  the  blood,  iince  fo 
large  a quantity  of  fugar,  as  was  found  in  the  urine,  namely, 
twenty  ounces  a day,  could  not  have  previouily  cxifted  in  die 
blood  without  being  perceptible  to  the  tafle. 

November  1. — Air.  Hughes  diflolved  two  drams  of  nitre  in 
a pint  of  a decoftion  of  the  roots  of  afparagus,  and  added  to  it 
two  ounces  of  tindfure  of  rhubarb:  the  patient  took  a fourth 
part  of  this  mixture  every  five  minutes,  till  he  had  taken  rite 
whole. — In  about  naif  an  hour  he  made  eighteen  ounces  of 
water,  which  was  very  manifeftly  tinged  with  die  rhubarb; 
the  fmeil  of  afparagus  was  doubtful. 

He  then  loft  four  ounces  of  blood,  the  ferum  of  which  was 
not  fo  opake  as  that  drawn  before,  but  of  a yeliovviih  cart, 
as  the  ferum  ol  tire  blood  ufually  appears. 

Paper,  dipped  three  or  four  times  in  the  tinged  urine,  and 
dried  again,  did  not  fcintillate  when  it  was  let  on  tire  ; but 
when  the  flame  was  blown  out,  the  hre  ran  along  the  paper  ter 
half  an  inch;  which,  when  tlie  lame  paper  was  unimpregnated, 
it  would  not  do;  nor  when  the  fame  paper  was  dipped  in  urine 
made  before  he  took  the  nitre,  and  dried  in  the  fame  manner. 

Paper,  dipped  in  the  ferum  of  the  blood,  and  dried  in  the  lame 
manner  as  in  the  urine,  did  not  fcintillate  when  the  flame  was 

blown 


Sect.  XXIX.  5.  RETROGRADE  ABSORBENTS.  237 

blown  out,  but  burnt  exactly  in  the  fame  manner  as  the  fame 
-paper  dipped  in  the  ferum  of  blood  drawn  from  another  perfon. 

This  experiment,  which  is  copied  from  a letter  of  Air. 
Hughes,  as  well  as  the  former,  deems  to  evince  the  exiiience 
of  another- pa ITage  from  the  inteftines  to  the  bladder,  in  this 
difeafe,  befides  that  of  the  fanguiterous  fyftem;  and  coincides 
with  the  curious  experiment  related  in  left  ion  the  third,  ex- 
cept that  the  fmell  of  the  afparagus  was  not  here  perceived, 
owing  perhaps  to  tire  roots  having  been  made  ufe  of  iriftead  of 
:the  heads. 

The  riling  in  the  throat  of  this  patient,  and  the  twitchings 
of  his  limbs,  feern  to  indicate  forne  llmiiarity  between  the  dia- 
betes and  the  hyfteric  difeafe,  befides  the  great  flow  of  pale 
-urine,  which  is  common  to  them  both. 

Perhaps,  if  the  mefenteric  glands  were  nicely  infpefted  in  the 
di  heft  ions  of  thefe  patients,  and  if  the  thoracic  duft,  and  the 
•larger  branches  of  the  iafteals,  and  if  the  lymphatics  which 
aiife  from  the  bladder,  were  well  examined  by  injeftion,  or 
by  the  knife,  the  caufe  of  diabetes  might  be  more  certainly 
•underftood. 

The  opium  alone,  and  the  opium  with  rhe  rofln,  feem  much 
to  have  ferved  this  patient,  and  might  probably  have  effefted 
a cure,  if  the  difeafe  had  been  flighter,  or  the  medicine  had 
been  exhibited  before  it  had  been  confirmed  by  habit  during 
:the  feven  months  it  had  continued.  The  increafe  of  the  quan- 
tity of  water  on  beginning  the  large  dofes  of  rofin,  was  probti- 
-bly  owing  to  his  omitting  the  morning  dofes  of  opium. 

V.  The  Phenomena  of  Dropfes  explained. 

I.  Some  inebriates  have  their  paroxyfms  of  inebriety  termi- 
•nated  by  much  pale  urine,  or  profufe  fvveats,  or  vomiting,  or 
ftools ; others  have  their  paroxyfms  terminated  by  ftupor,  or 
ileep,  without  the  above  evacuations. 

The  former  kind  ofthele  inebriates  have  been  obferved  to  be 
more  liable  to  diabetes  and  dropfy  ; and  the  latter  to  gout,  gra- 
.vel  and  leprofy.  Evoe  ! attend  ve  bacchanalians  ! ftart  at  this 
dark  train  of  evils,  and,  amid  your  immodeit  jefts,  and  ideot 
daughter,  recollect, 

Quem  Deus  vult  perdere,  prius  dementat. 

In  thofe  who  are  fubjeft  to  diabetes  and  dropfy,  the  abfor- 
bent  veflfels  are  naturally  more  irritable  than  the  latter;  and  by 
being  frequently  difturbed,  or  inverted  by  violenc  ftimulus,  and 
by  their  too  great  fympathy  with  each  other,  they  become  at 
length  either  entirely  paralytic,  or  are  only  l'ufceptible  of  mo- 
tion 


233  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  5. 

tion  from  the  ftimulus  of  very  acrid  materials ; as  every  part 
of  the  body,  after  having  been  ufed  to  great  irritations,  be- 
comes lefs  affedred  by  fmaller  ones.  Thus  we  cannot  diftin- 
guifh  objedts  in  the  night,  for  fome  time  after  we  come  out 
of  a ftrong  light,  though  the  iris  is  prefentiy  dilated:  and  the 
air  of  a hammer  evening  appears  cold,  after  we  have  been  ex- 
pofed  to  the  heat  of  the  day. 

There  are  no  cells  in  the  bodv,  where  cropfv  may  not  he 
produced,  if  the  lymphatics  ceafe  to  abforb  that  mucilaginous 
fluid,  which  is  perpetually  depoiited  in  them,  tor  the  purpofe 
of  lubricating  their  furfaces. 

If  the  lymphatic  branch,  which  opens  into  the  cellular 
membrane,  either  does  its  office  imperfectly,  or  not  s.t  all; 
thefe  cells  become  replete  with  a mucilaginous  fluid,  which,  af- 
ter it  has  ftagnated  fome  time  in  the  cells,  will  .coagulate  over 
tire  fire ; and  is  erroneoufly  cailed  water.  Wherever  the  feat 
of  this  difeafe  is,  (unlefs  in  the  lungs  or  other  pendent  viu  era) 
the  mucilaginous  liquid  above  mentioned  will  fubfide  to  the 
moft  depending  parts  of  the  bodv,  as  the  feet  and  legs,  when 
thofe  are  lower  than  the  head  and  trunk ; for  all  thefe  cells 
have  communications  with  each  other. 

When  the  cellular  abforbents  are  become  infenfible  to  their 
ufual  irritations,  it  raeft  frequently  happens,  but  not  always, 
that  the  cutaneous  branch  oi  abforbents,  which  is  ltricfly  af- 
fociated  with  them,  1 offers  the  like  inability.  And  then,  as 
no  water  is  abforbed  from  the  atmofphere,  the  urine  is  not 
only  lefs  diluted  at  the  time  of  its  fecretion,  and  confequently 
in  lefs  quantity  and  higher  coloured;  but  great  thirft  is  at  the 
fame  time  induced,  for  as  no  water  is  abforbed  from  the  atmof- 
phere to  dilute  the  chyle  and  blood,  the  ladleals  and  other  ab- 
forbent  veffels,  which  have  not  loft  their  powers,  are  excited 
into  more  confiant  or  more  violent  adlion,  to  fupply  this  defi- 
ciency ; whence  the  urine  becomes  (till  lels  in  quantity,  and 
of  a deeper  colour,  and  turbid,  like  the  yolk  of  an  egg,  owing 
to  a greater  abforption  of  its  thinner  parts.  From  this  ilronger 
action  of  thofe  abforbents,  which  (till  retain  their  irritabi- 
lity, the  fat  is  alfo  abforbed,  and  the  whole  body  becomes  ema- 
ciated. This  incrcafed  exertion  of  fome  branches  of  the  lym- 
phatics, while  others  are  totally  or  partially  paralytic,  is\re- 
iembled  by  what  conflantly  occurs  in  the  hemiplagia ; when 
the  patient  has  loft  the  ufe  of  his  limbs  on  one  fide,  he  is  in- 
ceffantly  moving  thofe  of  the  other:  for  the  moving  power, 
not  having  acceis  to  the  paralytic  limbs,  becomes  redundant  in 
thofe  which  are  notdifeafed. 

The  paucity  cf  urine  and  thirft  cannot  be  explained  from  a 

greater 


Sect.  XXIX.  5.  RETROGRADE  ABSORBENTS.  239 

greater  quantity  of  mucilaginous  fluid  being  depofited  in  the 
cellular  membrane : for  though  thefe  fymptoms  have  continu- 
ed many  weeks,  or  even  months,  this  collection  frequently 
does  not  amount  to  more  than  very  few  pints.  Hence  alfo  the 
difficulty  of  promoting  copious  fweats  in  anafarca  is  account- 
ed for,  as  well  as  the  great  third,  paucity  of  urine,  and  lofs 
of  fat ; lince,  when  the  cutaneous  branch  of  abforbents  is  pa- 
ralytic, or  nearly  fo,  there  is  already  too  fmall  a quantity  of 
aqueous  fluid  in  the  blood:  nor  can  thefe  torpid  cutaneous 
lymphatics  be  readily  excited  into  retrograde  motions. 

Hence,  likewife,  we  underhand  why,  in  the  afcites  and  fome 
other  dropiies,  there' is  often  no  third,  and  no  paucity  of  urine; 
in  thefecafes  the  cutaneous  abforbents  continue  to  do  their  office. 

Some  have  believed,  that  dropdes  were  occadoned  by  the  in- 
ability of  the  kidneys,  from  having  only  obferved  the  paucity 
of  urine;  and  have  thence  laboured  much  to  obtain  diuretic 
medicines;  but  it  is  daily  obfervable,  that  thofe  who  die  of  a 
total  inability  to  make  water,  do  not  become  droplical  in  con- 
fequence  of  it:  Fernelius  mentions  one,  who  laboured  under 
a perfect  fuppreflion  of  urine  during  twenty  days  before  his 
death,  and  yet  had  no  fymptoms  of  dropfy.  Pathol.  1.  vi.  c.  8. 
From  the  fame  idea  many  phyficians  have  redrained  their  pa- 
tients from  drinking,  though  their  third  has  been  very  urgent  ; 
and  fome  cafes  have  been  published,  where  this  cruel  regimen 
has  been  thought  advantageous  ; but  others  of  nicer  oblerva- 
tion  are  of  opinion,  that  it  has  always  aggravated  the  didrefTes 
of  the  patient ; and  though  it  has  abated  his  fwellings,  yet,  by 
inducing  a fever,  it  has  hadened  his  diflbiudon.  See  Tranfac- 
tions  of  the  College,  London,  vol.  ii.  p.  235.  Cafes  of  Dropfy, 
bv  Dr.  G.  Baker. 

The  cure  of  anafarca,  fo  far  as  refpedfs  the  evacuation  of 
the  accumulated  fluid,  coincides  with  the  idea  of  the  retrograde 
action  of  the  lymphatic  fyflem.  It  is  well  known  that  vomits, 
and  other  drugs,  which  induce  ficknefs  or  naufea,  at  the  fame 
time  that  they  evacuate  the  domach,  produce  a great  abforp- 
tion  of  die  lymph  accumulated  in  the  cellular  membrane.  In 
the  operation  of  a vomit,  not  only  the  motions  of  the  domach 
and  duodenum  become  inverted,  but  alfo  thofe  of  the  lympha- 
tics and  ladteals,  which  belong  to  them ; whence  a great  quan- 
tity of  chyle  and  lymph  is  perpetually  poured  into  the  domach 
and  intedines,  during  the  operation,  and  evacuated  by  the 
mouth.  Now,  at  due  fame  time,  other  branches  of  the  lym- 
phatic fydem,  viz.  thofe  which  open  on  the  cellular  membrane, 
are  brought  into  more  energetic  addon,  by  the  fymparhy  above 
mentioned,  and  an  increafe  of  their  abforptien  is  produced. 

Hence, 


240  RETROGRADE  ABSORBENTS-  Sect.  XXIX.  5, 

Hence,  repeated  vomits,  and  cupreous  falts,  and  fmall  dofes 
of  fquill  or  foxglove,  are  fo  efficacious  in  this  difeafc.  And  as 
draftic  purges  adt  alfo  by  inverting  the  motions  of  the  laCfeak, 
and  thence  the  other  branches  of  lymphatics  are  induced  into 
more  powerful  natural  action,  by  fympathy,  and  drink  up  the 
fluids  from  all  the  cells  of  the  body ; and  by  their  anaflomofe^, 
pour  them  into  the  laCteal  branches;  which,  by  their  inverted 
adlions,  return  them  into  the  inteftines  ; and  they  are  thus  eva- 
cuated from  the  body.  Thefe  purges  alfo  are  ufed  with  l'uc- 
cefs  in  difchargmg  the  accumulated  fluid  in  anafarca. 

II.  The  following  cafes  are  related  with  deiign  to  afeertain 
the  particular  kinds  of  dropfy  in  which  the  digitalis  purpurea, 
or  common  foxglove,  is  preferable  to  fquill,  or  other  evacu- 
ants,  and  were  flrft  publilhed  in  1780,  in  a pamphlet  entitled 
Experiments  on  mucilaginous  and  purulent  Matter,  &c.  Cadell. 
London.  Other  cafes  of  dropfy,  treated  with  digitalis,  were 
afterwards  publilhed  by  Dr.  Darwin,  in  the  Medical  Tranfac- 
tions,  vol.  iii.  in  which  there  is  a miflake  in  refpeCt  to  the 
<k>fe  of  the  powder  of  foxglove,  which  lliould  have  been  from 
five  grains  to  one,  inflead  ot  from  five  grains  to  ten. 

Anafarca  cf  the  Lungs. 

1.  A lady,  between  forty  and  fifty  years  of  age,  had  beer,  . 
indifpofed  fome  time,  was  then  feized  with  cough  and  fever, 
and  afterwards  expedlorated  much  digefted  mucus.  This  ex- 
pectoration fuddenly  ceafed,  and  a confiderable  difficulty  of 
•breathing  fu perverted,  with  a pulie  very  irregular  both  in  velocity 
and  ftrength  ; fhe  was  much  diftrfled  at  firfl  lying  down,  and 
at  firfl: riling;  but  after  a minute  or  two,  bore  either  ot  thofe 
attitudes  with  eafe.  She  had  no  pain  or  numbnefs  in  her  arms ; 
fhe  had  no  hedtic  fever,  nor  any  cold  thiverings,  and  the  urine 
was  indue  quantity,  and  of  the  natural  colour. 

Thedifficultv  of  breathing  was  twice  confiderahly  relieved  by 
fmall  dofes  of  ipecacuanha,  which  operated  upwards  and  down- 
wards, but  recurred  in  a few  days  : fhe  was  then  dire  died  a de- 
coCfion  of  foxglove,  (digitalis  purpurea)  prepared  bv  boiling 
four  ounces  of  the  frefh  leaves  from  two  pints  of  water  to  one 
pint;  to  which  was  added  two  ounces  ot  vinous  fpirit:  fhe 
took  three  large  fpoonluls  of  this  mixture  every  two  hours, 
till  fhehad  taken  it  four  times  ; a continued  ficknels  fupervened, 
with  frequent  vomiting,  and  a copious  flow  of  urine;  thele 
evacuations  continued,  at  intervals,  for  two  or  three  days,  and 
relieved  the  difficulty  of  breathing.  She  had  fome  relapl'es  at- 
tei  wards,  which  were  again  relieved  by  the  repetition  of  the 
decodiion  of  foxglove. 


2.  A 


sect.  XXIX.  5-  RETROGRADE  ABSORBENTS:  -4? 

2.  A gentleman,  about  fixty  years  of  age,  who  had  been 
addicted  to  an  immoderate  ufe  of  fermented  liquors,  and  had 
been  very  corpulent,  gradually  loft  his  ftrength  and  flefh,  had 
great  difficulty  of  breathing,  with  legs  fomevyhat  fwelled,  and 
a very  irregular  pulfe.  He  was  very  much  diftreffied  at  ftrft 
lying  down,  and  at  ftrft  riftng  from  his  bed ; yet  in  a minute  or 
two  was  eafy  in  both  thofe  attitudes.  He  made  ftraw -coloured 
urine  in  due  quantity,  and  had  no  pain  ornumbnefs  of  his  arms. 

He  took  a large  fpoonful  of  the  decoction  of  foxglove,  as 
above,  every  hour,  for  ten  or  twelve  fucceffive  hours;  had  in- 
cefiant  ftcknefs  for  about  two  days,  and  palled  a large  quantity 
of  urine ; upon  which  his  breath  became  quite  eafy,  and  the 
fwelling  of  his  legs  fubftded ; but  as  his  whole  conftitution  was 
already  finking  from  the  previous  intemperance  of  his  life,  lie 
did  not  furvive  more  than  three  or  four  months. 

Hydrops  Pericardii. 

3.  A gentleman  of  temperate  life  and  iedulous  application  to 
bulinefs,  between  thirty  and  forty  years  of  age,  had  long  been 
fubjeftt,  at  intervals,  to  an  irregular  pulfe  : a few  months  ago 
he  became  weak,  with  difficulty  of  breathing,  and  dry  cough. 
In  this  fttuation  a phyftcian  of  eminence  directed  him  to  ab- 
ftain  from  all  animal  food  and  fermented  liquor,  during  which 
regimen  all  his  complaints  increafed  ; he  now  became  emaci- 
ated, and  totally  loft  his  appetite ; his  pulfe  very  irregular,  both 
in  velocity  and  ftrength  ; with  great  difficulty  of  breathing, 
and  fome  fwelling  of  his  legs ; yet  he  could  lie  down  horizon- 
tally in  his  bed,  though  he  got  little  fleep,  and  pafted  a due 
quantity  of  urine,  and  of  the. natural  colour;  no  fuilnefs  or 
hardnefs  could  be  perceived  about  the  region  of  the  liver;  and 
he  had  no  pain  or  numbnefs  in  his  arm. 

One  night  he  had  a moft  profufe  fweat  all  over  his  body  and 
limbs,  which  quite  deluged  his  bed,  and  for  a day  or  two  fome- 
what relieved  his  difficulty  of  breathing,  and  his  pulfe  became 
lefs  irregular:  this  copious  fweat  recurred  three  or  four  times 
at  the  intervals  of  five  or  fix  days,  and  repeatedly  alleviated  his 
fymptoms. 

He  was  directed  one  large  fpoonful  of  the  above  decofttion 
of  foxglove  every  hour,  till  it  procured  fome  confiderable  eva- 
cuation: after  he  had  taken  it  eleven  fucceffive  hours,  he  had 
a few  liquid  ftools,  attended  with  a great  flow  of  urine,  which 
laft  had  a dark  tinge,  as  if  mixed  with  a few  drops  of  blood: 
he  continued  fick  at  intervals  for  two  days,  but  his  breath  be- 
came quite  eafy,  and  his  pulfe  quite  regular;  the  fwelling  of 
his  legs  difappeared,  and  his  appetite  and  fieep  returned. 

He 


242  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  5. 

He  then  took  three  grains  of  white  vitriol  twice  a day.  with 
fome  bitter  medicines,  and  a grain  of  opium,  with  five  grains  of 
rhubarb,  every  night;  was  advifed  to  eat  flefh  meat,  and  fpice, 
as  his  ftomach  would  bear  it,  with  finall  beer,  and  a few  gi  *ftes 
of  wine;  and  had  iffues  made  in  his  thighs;  and  has  fullered 
no  ralapfe. 

4.  A lady,  about  fifty  years  of  age,  had  for  fome  weeks 
great  difficulty  of  breathing,  with  very  irregular  pulfe,  and 
confiderable  general  debility ; fhe  could  iie  down  in  bed,  and 
the  urine  was  in  due  quantity  and  of  the  natural  colour,  and  ; 
file  had  no  pain  or  numbnefs  of  her  arms. 

She  took  one  large  fpoonful  of  the  above'decocfion  of  fox- 
glove every  hour,  for  ten  or  twelve  fucceffive  hours  ; was  fick, 
and  made  a quantity  of  pale  urine  for  about  two  davs.  and  was 
quite  relieved,  both  of  the  difficulty  of  breathing,  and  the  irre- 
gularity of  her  pulfe.  She  then  took  a grain  of  opium,  and  five 
grains  of  rhubarb,  every  night,  for  many  weeks,  with  fome  flight 
chalybeate  and  bitter  medicines,  and  has  faltered  no  rclapfe. 

Hydrops  Thorajis. 

5.  A tradefman,  about  fifty  years  of  age,  became  weak 
and  fiiort  of  breath,  efpecially  on  increafe  of  motion,  with 
pain  in  one  arm,  about  the  infertion  of  the  biceps  inufeie.  He 
o'oferved  he  fometimes  in  the  night  made  an  unufual  quantity 
of  pale  water.  He  took  calomel,  alum,  and  Peruvian  bark, 
and  all  his  fymptoms  increafed:  his  legs  began  to  fwell  confi- 
dtfrably  ; his  breath  became  more  difficult,  and  he  could  nor  lie 
down  in  bed;  but  all  this  time  he  made  a due  quantity  of 
firaw-coloured  water. 

The  decodtlon  of  foxglove  was  given  as  in  the  preceding 
cafes,  which  operated  chiefly  by  purging,  and  feemed  to  re-' 
lieve  his  breath  for  a dav  or  two,  but  alio  feemed  to  contribute 
to  weaken  him.  He  became,  after  fome  weeks,  univerfallv 
dropfical,  and  died  comatous. 

6.  A young  ladv  of  delicate  conftitution,  with  light  eve* 
and  hair,  and  who  had  perhaps  lived  too  abftemioufly.  both  in 
reipedl  to  the  quantity  and  quality  of  what  fhe  eat  and  drank, 
wasfeized  with  great  difficulty  of  breathing,  fo  as  to  threaten 
immediate  death.  Her  extremities  were  quite  cold,  and  her 
breath  felt  cold  to  the  back  of  ones  hand.  She  had  no  lweat, 
nor  could  lie  down  for  a Angle  moment ; and  had  previouily, 
and  at  prefent,  complained  of  great  weaknefs  and  pain,  and 
numbnefs  of  both  her  arms  ; had  no  fweiiing  of  her  lets.  r.o 
third,  water  in  due  quantity  and  colour.  Her  lifter,  about  a 
year  before,  was  afflidfed  with  limilar  fymptoms,  was  repeat- 
edly blooded,  and  died  univerfally  dropfical. 

A grain 


SficT.XXlX.  5.  RETROGRADE  ABSORBENTS.  243 

A grain  of  opium  was  given  immediately,  and  repeated  eve- 
ry fix  hours  with  evident  and  amazing  advantage ; afterwards 
a blifter,  with  chalybeates,  bitters,  and  eflential  oils,  were  exhibit- 
ed, but  nothing  had  fuch  eminent  eftecft  in  relieving  the  difficulty 
of  breathing  and  coldnefs  of  her  extremities  as  opium  ; by  the 
ufe  of  which,  in  a few  weeks,  the  perfectly  regained  her  health, 
and  has  buffered  no  relapfe. 

AJ cites. 

A young  lady,  of  delicate  conftitution,  having  been  expof- 
ed  to  great  fear,  cold,  and  fatigue,  by  the  overturn  of  a chaife 
in  the  night,  began  with  pain  and  tumour  in  the  right  hypochon- 
drium : in  a few  months  a fluctuation  was  felt  throughout  the 
whole  abdomen,  more  diftinctly  perceptible  indeed  about  the 
region  of  the  ftomafch;  fince  the  integuments  of  the  lower  part 
of  the  abdomen  generally  become  thickened  in  this  difeafc  by  a 
degree  of  anafarca.  Her  legs  were  not  fvvelled,  no  thirft,  wa- 
ter in  due  quantity  and  colour. — She  took  the  foxglove  fo  as  to 
induce  ticknefs  and  ftools,  but  without  abating  the  fweliing,  and 
was  obliged,  at  length,  to  fubrnit  to  the  operation  of  tapping. 

8.  A man  about  lixty-feven,  who  had  long  been  accuftomed 
to  fpirituous  potation,  had  fome  time  laboured  under  afcites  ; 
his  legs  fomewhat  fwelled ; his  breath  eafy  in  all  attitudes  ; no 
appetite ; great  thirft ; urine  in  exceedingly  frnall  quantity,  very 
deep  coloured,  and  turbid ; pulfe  equal.  He  took  the  foxglove 
in  fuch  quantity  as  vomited  him,  and  induced  ficknets  for  two 
days ; but  procured  no  flow  of  urine,  or  diminution  of  his  fwel- 
ling ; but  was  thought  to  leave  him  conflderably  weaker. 

g.  A corpulent  man,  accuftomed  to  large  potation  of  fer- 
mented liquors,  had  vehement  cough,  difficult  breathing,  ana- 
farca of  his  legs,  thighs  and  hands,  and  conftde-rable  tumour,  with 
evident  fluctuation  of  his  abdomen ; his  pulfe  was  equal ; his 
urine  in  frnall  quantity,  of  deep  colour,  and  turbid.  Thefe 
fwellings  had  been  twice  conflderably  abated  by  draftic  cathar- 
tics. He  took  three  ounces  ot  a decoction  ot  foxglove  (made 
by  boiling  one  ounce  of  the  frefli  leaves  in  a pint  ot  water) 
every  three  hours,  for  two  whole  days ; it  then  began  to  vomit 
and  purge  him  violently,  and  promoted  a great  flow  of  urine; 
he  was  by  thefe  evacuations  completely  emptied  in  twelve  hours. 
After  two  or  three  months  all  thefe  fymptoms  returned,  and 
were  again  relieved  by  the  ufe  of  the  foxglove ; and  thus,  in  the 
fpace  ot  about  three  years,  he  was  about  ten  times  evacuated, 
and  continued  all  that  tithe  his  ufual  potations:  excepting  at 
firft,  the  medicine  operated  only  by  urine,  and  did  not  appear 
conflderably  to  weaken  him.  The  laft  time  he  took  it,  it  had 

K k no 


244  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  5. 

no  effect;-  and  a few  weeks  afterwards  he  vomited  a great 
quantity  of  blood,  and  expired. 

QUERIES. 

1.  As  the  firft  fix  of  thefe  patients  had  a due  difeharge  of 
urine,  and  of  the  natural  colour,  was  not  the  feat  of  the  difeafe 
confined  to  fome  part  of  the  thorax,  and  the  fvvelling  of  the 
legs  rather  a fymptom  of  the  obftrudted  circulation  of  the  blood, 
than  ot  a paralvfis  of  the  cellular  lymphatics  of  thofe  parts? 

2.  When  the  original  difeafe  is  a general  anafarca,  do  not 
the  cutaneous  lymphatics  always  become  paralytic  at  tire  fame 
time  with  the  cellular  ones,  by  their  greater  fvmpathv  with 
each  Other ; and  hence  the  paucity  of  urine,  and  the  great  thiift 
diftinguifh  this  kind  ot  diopfy  ? 

3.  in  the  anafarca  of  the  lungs,  when  the  difeafe  is  pot  very 
great,  though  the  patients  haveconfiderable  difficulty  of  breath- 
ing at  their  firft  lying  down,  yet  after  a minute  or  two  their  breath 
becomes  eafv  again  ; and  the  fame  occurs  at  their  firfl  rifing. 
Is  not  this  owing  to  the  time  neceffary  lor  the  fluid  in  the  cells 
of  the  lungs  to  change  its  place,  fo  as  the  ieaft  to  incommode 
refpiration  in  the  new  attitude  ? 

4.  In  tire  dropfy  of  the  pericardium,  does  not  the  patient 
bear  tire  horizontal  or  perpendicular  attitude  with  equ.. ! c^le  ? 
Does  this  circumftance  diftinguifh  the  dropfy  oi  the  pericardi- 
um from  that  of  the  lungs  and  of  the  thorax  ? 

5.  Do  the  univerfal  fweats  diftinguifh  the  dropfy  of  the  pe- 
ricardium, or  of  the  thorax?  and  thofe,  which  cover  the  upper 
parts  of  the  body  only,  the  anafarca  of  the  lungs? 

6.  When,  in  tire  dropfy  of  the  thorax,  the  patient  endeavours 
to  lie  down, .does  not  the  extravafated  fluid  comprels  the  upper 
parts  of  the  bronchia,  and  totally  preclude  the  accefs  of  air  to 
every  part  of  the  lungs,  whilft  in  the  perpendicular  attitude 
the  inferior  parts  of  the  lungs  only  are  coinpreffsd?  Does  net 
fomethinp'  fimilar  to  this  occur  in  the  anafarca  of  the  lungs 
when  the  difeafe  is  very  gieat,  and  thus  prevent  thole  patients 
alio  from  lying  down  ? 

7.  As  a principal  branch  of  the  fourth  cervical  nerve  of  the 
left  fide,  after  .having  joined  a branch  ot  the  third  and  ot  the  te- 
cond  cervical  nerves,  defeending  between  the  fubclavian  vein 
and  artery,  is  received  in  a groove  formed  for  it  in  the  pericar- 
dium, and  is  obliged  to  make  a coniiderable  turn  outwards  to 
go  'over  the  prominent  part  of  it,  where  the  point  of  the  head 
is*  lodged,  in  its  courfe  to  the  diaphragm ; and  as  the  other  phre- 
nic nerve  ot  the  right  fide  has  a ftraigirt  ccui  fe  to  the  diaphragm  ; 
and  as  many  other  coniiderable  branches  of  this  fourth  pair  of 

cervical 


Sect.  XXIX.  6.  RETROGRADE  ABSORBENTS.  245 

.cervical  nerves  are  fpread  on  the  arms ; does  not  a pain  in  the 
left  arm  diftinguifh  a difeafe  of  the  pericardium,  as  in  the  a gin  a 
pedforis,  or  in  the  dropfy  of  the  pericardium?  and  does  not  a 
pain  or  weaknefs  in  both  arms  difHnguifh  the  dropfy  of  the  tho- 
rax ? 

8.  Do  not  the  dropfies  of  the  thorax  anu  pericardium  fre- 
quently exift  together,  and  thus  add  to  the  uncertainty  and  fa- 
tality of  the  difeafe  ? 

9.  Might  not  the  foxglove  be  ferviceable  in  hydrocephalus 
internus,  in  hydrocele,  and  in  white  fwellings  of  the  joints  ? 

-V I.  Of  Cold  Sweats. 

There  have  been  hiftories  given  of  chronical  immoderate 
■fweatings,  which  bear  fome  analogy  to  the  diabetes.  Dr.  Wil- 
lis mentions  a lady,  then  living,  whole  fweats  were,  for  many 
years,  fo  profufe,  that  all  her  bed-clofhes  were  not  only  moif- 
tened,  but  deluged  with  them  every  night;  and  that  many  oun- 
ces, and  fometimes  pints,  of  this  fweat,  were  received  in  veflfels 
properly  placed,  as  it  trickled  down  her  body.  He  adds,  that 
fhe  had  great  thirfl,  had  taken  many  medicines,  and  iubmitted  to 
various  rules  of  life,  and  changes  of  climate,  but  ftill  continued 
to  have  thefe  immoderate  fweats.  Pharmac.  ration,  de  fudore 
anglico. 

Dr.  Willis  has  alfo  obferved,  that  the  fudor  anglicanus  which 
appeared  in  England  in  1483,  and  continued  till  1551,  wras,  in 
fome  refpedts,  Cmilar  to  the  diabetes;  and,  as  Dr.  Caius,  who 
faw  this  difeafe,  mentions  the  vifcidity,  as  well  as  the  quantity 
of  thefe  fweats,  and  adds,  that  the  extremities  were  often  cold 
when  the  internal  parts  were  burnt  up  with  heat  and  third,  with 
great  and  fpeedy  emaciation  and  debility,  there  is  great  reafon  to 
believe,  that  the  fluids  were  abforbed  from  the  cells  of  the  body 
by  the  cellular  and  cyftic  branches  of  the  lymphatics,  and  poured 
on  the  fkin  by  the  retrograde  motions  of  the  cutaneous  ones. 

Sydenham  has  recorded,  in  the  ftationarv  fever  of  the  year 
1685,  the  vifcid  fweats  flowing  from  the  head,  which  w'ere 
probably  from  the  fame  fource  as  thofe  in  the  fweating  plague 
above  mentioned. 

It  is  very  common,  in  dropfies  of  the  chefl  or  lungs,  to  have 
the  difficulty  of  breathing  relieved  by  copious  fweats,  flowing 

from  the  head  and  neck.  Mr.  P , about  fifty  years  of  age, 

had,  for  many  weeks,  been  afilidted  with  anafarca  of  his  legs 
and  thighs,  attended  with  difficulty  of  breathing;  and  had  re- 
peatedly been  relieved  by  fquill,  other  bitters,  and  chalybeates. 
One  night  the  difficulty  of  breathing  became  fo  great,  that  it  was 
.thought  he  mult  have  expired ; but  fo  copious  a fweat  came  out 


246  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  6. 

of  his  head  and  neck,  that  in  a few  hours  fome  pints,  by  efii- 
mation,  were  wiped  off  from  thofe  parts,  and  his  breath  was 
for  a time  relieved.  This  dyipncea  and  thefe  fweats  recurred  at 
intervals,  and  after  fome  weeks  he  ceafed  to  exift.  The  fkin 
of  his  head  and  neck  felt  cold  to  the  hand,  and  appeared  pale 
at  the  time  thefe  fweats  flowed  fo  abundantly ; which  is  a 
proof,  that  they  were  produced  by  an  inverted  motion  of  the 
abforbents  of  thofe  parts:  for  fweats,  which  are  the  confe- 
quence  ot  an  increased  a£tion  of  the  fanguiferous  fyftem,  are 
always  attended  with  a warmth  of  the  fkin,  greater  than  is 
natural,  and  a more  florid  colour ; as  the  fweats  from  exer- 
cife,  or  thofe  that  lucceed  the  cold  fits  of  agues.  Can  any 
one  explain  how  thefe  partial  fweats  fhould  relieve  the  difficul- 
ty of  breathing  in  anafarca,  but  by  fuppofing  that  the  pulmo- 
nary branch  of  abforbents  drank  up  the  fluid  in  the  cavity  of 
the  thorax,  or  in  the  cells  of  the  lungs,  and  threw  it  on  the 
fkin,  by  the  retrograde  motions  of  the  cutaneous  branch:  for, 
if  we  could  fuppofe  that  the  increafed  adtion  of  the  cutane- 
ous glands  or  capillaries  poured  upon  the  fkin  this  fluid,  pre- 
vioufly  abforbed  from  the  lungs ; why  is  not  the  whole  furface 
of  the  body  covered  with  fweat?  why  is  not  the  fkin  warm? 
Add  to  this,  that  the  fweats  above  mentioned  were  clammy 
or  glutinous,  which  the  condenfed  perfpirable  matter  is  not; 
whence  it  would  l'eem  to  have  been  a different  fluid  from  that 
of  common  perfpiration. 

Dr.  Dobfon,  of  Liverpool,  has  given  a very  ingenious  ex- 
planation of  the  acid  fweats,  which  he  obferved  in  a diabetic 
patient — he  thinks  part  of  the  chyle  is  fecreted  by  the  fkin, 
and  afterwards  undergoes  an  acetous  fermentation. — Can  the 
chyle  get  thither,  but  by  an  inverted  motion  of  the  cutaneous 
lymphatics,  in  the  fame  manner  as  it  is  carried  to  the  bladder, 
by  the  inverted  motions  of  the  urinary  lymphatics?  Medic. 
Obfervat.  and  Enq.  London,  vol.  5. 

Are  not  the  cold  fweats  in  fome  fainting  fits,  and  in  dying 
people,  owing  to  an  inverted  motion  of  the  cutaneous  lympha- 
tics ? for  in  thefe  there  can  be  no  increafed  arterial  or  glandu- 
lar action. 

Is  tite  difficulty  of  breathing,  arifing  from  anafarca  of  the 
lungs,  relieved  by  fweats  from  the  head  and  neck,  whilft  that 
difficulty  of  breathing,  which  arifes  from  a dropfy  of  the  tho- 
rax, or  pericardium,  is  never  attended  with  thele  fweats  of  the 
head?  and  thence  can  thefe  difeafes  bediftinguifhed  from  each 
other?  Do  the  periodic  returns  of  nocturnal  afthma  rife  from 
a temporary  dropfy  of  the  lungs,  collected  during  their  more 
torpid  ft  ate  in  found  fleep,  and  then  re-ablorbed  by  the  vehe- 
ment 


Sect. XXIX.  7.  RETROGRADE  ABSORBENTS.  247 

merit  efforts  of  the  difordered  organs  of  refpiration,  and  carri- 
ed off  by  the  copious  fweats  about  the  head  and  neck  ? 

More  extenhve  and  accurate  diffedtions  of  the  lymphatic  fyf- 
tetn  are  wanting  to  enable  us  to  unravel  thefe  knots  of  fcience. 

VII.  Tranflations  of  Matter,  of  Chyle , of  Milk,  of  Urine. 

Operation  of  purging  Drugs  applied  externally. 

1 . The  tranflations  of  matter  from  one  part  of  the  body  to 
another,  can  only  receive  an  explanation  from  the  dodtrine  of 
the  occafional  retrograde  motions  of  fome  branches  of  the 
lymphatic  fyflem : for  how  can  matter,  abforbed  and  mixed 
with  the  whole  mafs  of  blood,  be  fo  haftily  colledted  again  in 
any  one  part  ? and  is  it  not  an  immutable  law,  in  animal  bo- 
dies, that  each  gland  can  fecrete  no  other  but  its  own  proper 
fluid  ? which  is,  in  part,  fabricated  in  the  very  gland  by  an 
animal  procefs,  which  it  there  undergoes : of  theie  purulent 
tranflations  innumerable  and  very  remarkable  inftances  are 
recorded. 

2.  The  chyle,  which  is  feen  among  the  materials  thrown 
up  by  violent  vomiting,  or  in  purging  ftools,  can  only  come 
thither  by  its  having  been  poured  into  the  bowels  by  the  invert- 
ed motions  of  the  ladfeals:  for  our  aliment  is  not  converted 
into  chyle  in  the  ftomach  or  inteftines  by  a chemical  procefs, 
but  is  made  in  the  very  mouths  of  the  ladleals ; or  in  the  me- 
fenteric  glands ; in  the  fame  manner  as  other  fecreted  fluids  are 
made  by  an  animal  procefs  in  their  adapted  glands. 

Here  a curious  phenomenon  in  the  exhibition  of  mercury 
is  worth  explaining : — If  a moderate  dofe  of  calomel,  as  fix  or 
ten  grains,  be  fwallowed,  and  within  one  or  two  days  a cathar- 
tic is  given,  a falivation  is  prevented : but  after  three  or  four 
days,  a falivation  having  come  on,  repeated  purges  every  day, 
for  a week  or  two,  are  required  to  eliminate  the  mercury  from 
the  conftitution.  For  this  acrid  metallic  preparation,  being 
abforbed  by  the  mouths  of  the  ladleals,  continues,  for  a time, 
arrefted  by  the  melenteric  glands,  (as  the  variolous  or  vene- 
real poifons  fwell  the  fubaxillar  or  inguinal  glands :)  which, 
during  the  operation  of  a cathartic,  is  returned  into  the  intef- 
tines by  the  inverted  adlion  of  the  ladleals,  and  thus  carried 
out  of  the  fyflem. 

Hence  we  underftand  the  ufe  of  vomits  or  purges,  to  thofe 
who  have  lwallowed  either  contagious  or  poifonous  materials, 
even  though  exhibited  a day,  or  even  two  days,  after  fuch  acci- 
dents ; namely,  that  by  the  retrograde  motions  of  the  ladleals 
and  lymphatics,  the  material  ftill  arrefted  in  the  mefenteric,  or 
pther  glands,  may  be  eliminated  from  the  body. 


3.  Many 


24S  RETROGRADE  ABSORBENTS.  Sect. XXIX.  7. 

3.  Many  inftances  of  milk  and  chyle  found  in  ulcers,  are 
given  by  Haller,  El.  Phyfiol.  T.  vii.  p.  12,23.  which  admit  of 
no  other  explanation  than  by  fuppofing  that  the  chyle,  imbibed 
by  one  branch  of  the  abforhent  fydem,  was  carried  to  the  ulcer 
by  the  inverted  motions  of  another  branch  of  the  fame  fvftem. 

4.  Mrs.  P.  on  the  fecondday  after  delivery,  was  feizeu  with 
a violent  purging,  in  which,  though  opiates,  mucilages,  the 
bark,  and  tedacea  were  profufely  ufed,  continued  many  davs, 
till  at  length  the  recovered.  During  the  time  of  this  purging, 
no  milk  could  be  drawn  from  her  breads  ; but  the  flools  ap- 
peared like  the  curd  of  milk  broken  into  fmall  pieces.  In  this 
cafe,  was  not  the  milk  taken  up  from  the  follicles  of  the  pecto- 
ral glands,  and  thrown  on  the  inteftines,  by  a retrogreffion  of 
the  inteftinal  abforbents?  for  how  can  we  lor  a moment  fuf- 
pe£t  that  the  mucous  glands  of  the  inteftines  could  1'eparare 
pure  milk  from  the  blood?  Doctor  Smelly  has  obferved,  that 
loofe  Itools,  mixed  with  milk,  which  is  curdled  in  the  inteftines, 
frequently  relieves  the  turgelcency  of  the  breads  of  thofe  who 
ftudicully  repel  their  milk.  Cafes  in  Midwifery,  43,  No.  2.  1 . 

5.  j.  F.  Meckel  obferved  in  a patient  whole  urine  was  in 
fmall  quantity  and  high  coloured,  that  a copious  fweat  under 
the  arm-pits,  of  a perfectly  urinous  lined,  trained  tire  linen  ; 
which  ceafed  again  when  the  ufual  quantity  of  urine  was  dif- 
charged  by  the  urethra.  Here  wTe  mud  believe,  from  analogy, 
that  the  urine  was  firft  fecreted  in  the  kidneys,  then  re-abb  r- 
bed  by  the  increafcd  adtion  of  the  urinary  lymphatics,  and  lad- 
ly  carried  to  the  axillae  by  the  retrograde  motions  of  the  lym- 
phatic branches  ot  thofe  parts.  As  in  the  jaundice  it  is  m:et- 

.lary  that  the  bile  firould  firft  be  fecreted  by  the  liver,  and  re- 
ablorbed  into  the  circulation,  to  produce  the  yeliownefs  of  the 
fkin  ; as  was  formerly  demondrated  by  the  late  Dr.  Monro, 
(Edin.  Medical  ElTays)  and  if  in  this  patient  the  urine  had 
been  re-abforbed  into  the  mafs  of  blood,  as  die  bile  in  the  jaun- 
dice, why  was  it  not  detected  in  other  parts  ot  the  body  as  well 
as  in  the  arm-pits  ? 

6.  Cadrarticand  vermifuge  medicines,  applied  externally  to 
the  abdomen,  feem  to  be  taken  up  by  the  cutaneous  branch  of 
lymphatics,  and  poured  on  the  intedinesby  the  retrograde  mo- 
tions of  the  ladteals,  without  having  palled  the  circulation. 

For,  when  the  dradic  purges  are  taken  by  the  mouth,  they 
excite  the  ladteals  ot  the  inteftines  into  retrograde  motions,  as 
appears  from  the  chyle,  which  is  found  coagulated  among  the 
faeces,  as  was  fhewn  above,  (fedt.  2 and  4.)  And  as  the  cutaneous 
lymphatics  are  joined  with  the  indteals  of  the  inteftines,  by  fre- 
quent anadomofes,  it  would  be  more  extraordinary,  when  a 

llrong 


Sect.  XXIX.  8.  RETROGE.ADE  ABSORBENTS.  249 

flrong  purging  drug,  abforbed  by  the  fkin,  is  carried  to  the 
anaftomoftng  branches  of  the  laddeals  unchanged,  if  it  fliould 
not  excite  them  into  retrograde  adlion  as  efficacioufly  as  if  it  was 
taken  by  the  mouth,  and  mixed  with  the  food  of  the  ftomach. 

VIII.  Circumjlances  by  which  the  Fluids  that  are  ejfufed 

by  the  retrograde  Motions  of  the  abforbent  Vejfels  are 

diflinguljhed. 

1.  We  frequently  obferve  an  unufual  quantity  of  mucus  or 
other  fluids  in  fome  difeafes,  although  the  action  of  the  glands, 
by  which  thofe  fluids  are  feparated  from  the  blood,  is  not  unufu- 
ally  incveafed,  but  when  the  power  of  abfotption  alone  is  di- 
minifhed.  Thus  the  catarrhal  humour  from  the  noftrils  of  fome 
who  ride  in  frofty  weather,  and  the  tears  which  run  down  the 
cheeks  of  thole  who  have  an  obftrucftion  of  the  pundta  lacry- 
malia,  and  the  ichor  of  thofe  phagedenic  ulcers,  which  are 
not  attended  with  inflammation,  are  all  inftances  of  this  cir- 
eumftance. 

Thefe  fluids,  however,  are  eanly  diftinguifhed  from  others,  by 
their  abounding  in  ammoniacal  or  muriatic  falts;  whence  they 
' inflame  the  circumjacent  fkin  : thus  in  the  catarrh  the  upper 
lip  becomes  red,  and  fwelled  from  the  acrimony  of  the  mucus, 
and  patients  complain  of  the  faltnefs  of  its  tafte.  The  eyes  and 
cheeks  are  red  with  the  corrofive  tears,  and  the  ichor  of  fome 
herpetic  eruptions  erodes  far  and  wdde  the  contiguous  parts, 
and  is  pungently  fait  to  the  tafte,  as  fome  patients  have  in- 
formed me. 

Whilft,  on  the  contrary,  thofe  fluids  which  are  efFufed  by 
the  retrograde  adtion  of  the  lymphatics,  are  for  the  moft  part 
mild  "and  innocent;  as  water,  chyle,  and  the  natural  mucus: 
or  they  take  their  properties  from  the  materials  previoufly 
abforbed,  as  in  the  coloured  or  vinous  urine,  or  that  fcented 
with  afparagus,  defcribed  before. 

2.  Whenever  the  fecretion  of  any  fluid  is  increafed,  there 
is,  at  the  fame  time,  an  increafed  heat  in  the  part ; for  the  fe- 
ereted  fluid,  as  the  bile,  did  not  previoufly  exift  in  the  mafs 
of  blood,  but  a new  combination  is  produced  in  die  gland. 
Now,  as  folutions  are  attended  with  cold,  fo  combinations  are 

I attended  with  heat ; and  it  is  probable  the  fum  of  the  heat  given 
out  by  all  the  fecreted  fluids  of  animal  bodies,  may  be  the  caufe 
of  their  general  heat  above  that  of  the  atmofphere. 

Hence  the  fluids  derived  trorn  increafed  fecretions  are  readi- 
ly diftinguiihed  from  thofe  originating  from  the  retrograde  mo- 
tions of  the  lymphatics : thus  an.  incrcafe  of  heat,  either  in  the 
difeafed  parts,  or  diftufed  over  the  whole  body,  is  perceptible, 

when 


250  RETROGRADE  ABSORBENTS.  Sect.  XXIX.  9, 

when  copious  bilious  ftools  are  confequent  to  an  inflamed  liver, 
or  a copious  mucous  falivation  from  the  inflammatory  angina. 

3.  When  any  fecreted  fluid  is  produced  in  an  unufual  quan- 
tity, and  at  the  fame  time  the  power  of  abforption  is  incrcafed 
in  equal  proportion,  not  only  the  heat  of  the  gland  becomes 
more  intenfe,  but  the  fecreted  fluid  becomes  thicker  and  milder, 
its  thinner  and  faline  parts  being  re-abforbed : and  thefe  are  dif- 
tinguifhable  both  by  their  greater  confilfence,  and  bv  their  heat 
from  the  fluids,  which  are  effufed  by  the  retrograde  motions 
of  the  lymphatics ; as  is  obfervable  towards  the  termination  of 
gonorrhoea,  catarrh,  chincougb,  and  in  thofe  ulcers  which 
are  laid  to  abound  with  laudable  pus. 

4.  When  chyle  is  obferved  in  ftools,  or  among  the  materi- 
als ejedled  by  vomit,  we  may  be  confident  it  rauft  have  been 
brought  thither  by  the  retrograde  motions  of  the  ladteais;  for 
chyle  does  not  previoufly  exift  amid  the  contents  of  the  intef- 
tities,  but  is  made  in  the  very  mouths  of  the  ladteals,  as  was 
before  explained. 

5.  When  chyle,  milk,  or  other  extraneous  fluids  are  found 
in  the  urinary  bladder,  or  in  any  other  excretory  receptacle  of 
a gland;  no  one  can  for  a moment  believe,  that  thefe  have 
been  collected  from  the  mafs  ot  blood  by  a morbid  lecretion, 
as  it  contradicts  all  analogy. 

Aurea  durse 

Mala  ferant  quercus?  Narcisco  floreat  alnus? 

Pinguia  corticibus  sudent  eiectra  myricre?  Virg. 

IX.  Retrograde  Motions  of  Vegetable  Juices. 

There  are  befides  fome  motions  of  the  fap  in  vegetables, 
which  bear  analogy  to  our  prefent  fubjeCt ; and  as  the  vege- 
table  tribes  are  by  many  philofophers  held  to  be  inferior  ani- 
mals, it  may  be  a matter  ol  curiolity  at  leaft  to  obferve,  that 
their  abforbent  veflfels  feem  evidently,  at  times,  to  be  capable 
of  a retrograde  motion.  Mr.  Perault  cut  off  a forked  branch 
of  a tree,  with  the  leaves  on  ; and  inverting  one  ot  the  forks 
into  a veffel  of  water,  obferved,  that  the  leaves  on  the  other 
branch  continued  green  much  longer  than  thofe  ot  a fimilar 
branch,  cut  oft  from  the  fame  tree;  which  thews,  that  the 
water  from  the  veffel  was  carried  up  one  part  of  the  forked 
branch,  by  the  retrograde  motion  of  its  veffels,  and  iupphed 
nutriment  fome  time  to  the  other  part  of  the  branch,  which 
was  out  of  the  water.  And  the -celebrated  Dr.  Hales  found, 
by  numerous  verv  accurate  experiments,  that  the  lap  ot  trees 
rofe  upwards  during  the  warmer  hours  of  the  dav,  and  in  part 
defeended  again  during  the  cooler  ones.  Vegetable  Statics. 


3fCT.XXIX.io.  RETROGRADE  ABSORBENTS.  25s 

It  is  well  known  that  the  branches  of  willows,  and  of  many 
other  trees,  will  either  take  root  in  the  earth,  or  engraft  on 
ether  trees,  fo  3s  to  have  their  natural  dire&ion  inverted,  and 
yet  flourifh  with  vigour. 

Dr.  Hope  has  alfo  made  this  pleafing  experiment,  after  the 
manner  of  Hales — he  has  placed  a forked  branch,  cut  from  one 
tree,  eretft  between  two  others ; then  cutting  off  a part  of  the 
bark  from  one  fork,  applied  it  to  a fnnilar  branch  of  one  of  the 
trees  in  its  vicinity,  and  the  fame  of  the  other  iork  ; fo  that  a 
tree  is  feen  to  grow  fufpended  in  the  air,  between  two  other 
trees,  which  fupply  their  fofter  friend  with  due  nourifhment. 

Miranturque  novas  ffondes,  et  non  suapoma. 

All  thefe  experiments  clearly  evince,  that  the  juices  of  ve- 
getables can  occallonally  pafs  either  upwards  or  downwards 
in  their  abforbent  fyftem  of  veflels. 

X.  Objections  anfwcred. 

The  following  experiment,  at  firft  view,  would  feem  to  in- 
validate this  opinion  of  the  retrograde  motions  of  the  lympha^ 
tic  veffels  in  fome  difeafes. 

About  a gallon  of  milk  having  been  given  to  an  hungry 
fwine,  he  was  fufFered  to  live  about  an  hour-,  and  was  then 
killed  by  a ftroke  or  two  on  his  head,  with  an  axe.  On  open- 
ing his  belly,  the  ladbeals  were  feen  well  filled  with  chyle ; on 
irritating  many  of  the- branches  of  them  with  a knife,  they  did 
not  appear  to  empty  themfeives  haftily  ; but  they  did  however 
carry  torwards  their  contents  in  a little  time. 

I then  palled  a ligature  round  feveral  branches  of  ladleals, 
and  irritated  them  much  with  a knife  beneath  the  ligature,  but 
could  not  make  them  regurgitate  their  contained  fluid  into  the 
bowels. 

I am  not  indeed  certain  that  the  nerve  was  not  at  the  fame 
time  included  in  the  ligature,  and  thus  the  lymphatic  rendered 
unirritable  or  lifelefs  ; but  this  however  is  certain,  that  it  is  not 
any  quantity  of  any  ftimulus,  which  induces  the  veffels  of 
animal  bodies  to  revert  their  motions;  but  a certain  quantity 
of  a certain  ftimulus,  as  appears  from  wounds  in  the  ftomach, 
which  do  not  produce  vomiting;  and  wounds  of  the  inteftines," 
which  do  not  produce  the  cholera  morbus. 

At  Nottingham,  a few  years  ago,  two  ftioemakers  quarrelled, 
and  one  ot  them,  with  a knife  which  they  ufe  in  their  occupa- 
tion, ftabbed  his  companion  about  the  region  of  the  ftomach. 
On  opening  the  abdomen  of  the  w'ounded  man  after  his  death, 
the  food  and  medicines  he  had  taken  were  in  part  found  in  the 

E l 


25 2 RETROGRADE  ABSORBENTS.  Sect.XXIX.i  i. 

cavity  of  the  belly,  on  the  outhde  of  the  bowels  ; and  there 
was  a wound  about  half  an  inch  tong  at  the  bottom  of  the  fto- 
mach;  which  1 iuppofe  was  diftended  with  liquor  and  food  at 
the  time  of  the  accident,  and  fner.ce  was  more-liable  to  be  in- 
jured at  its  bottom : but  dining  the  whole  time  he  lived,  which 
was  about  ten  days,  he  had  no  efforts  to  vomit,  nor  ever  even 
complained  of  being  fick  at  the  ftomach  ! Other  cafes,  limilar 
to  this,  are  mentioned  in  the  Bhilofophical  TranfaAions. 

Thus,  if  you  veliicate  the  throat  with  a feather,  naufea  is 
produced  ; if  you  wound  it  with  a pen-knife,  pain  is  induced, 
but  not  llckneis.  So  if  the  loles  of  the  feet  of  children  or  their 
arm-pits  are  tickled,  convulilve  laughter  is  excited,  which 
ceafes  the  moment  the  hand  is  applied,  fo  as  to  rub  them  more 
forcibly. 

The  experiment,  therefore,  above  related  upon  the  h Avals 
of  a dead  pig,  which  weie  included  in  a ftriA  ligature,  proves 
nothing;  as  it  is  not  the  quantity,  but  the  kind  of  ftimulus, 
which  excites  the  lymphatic  velfels  into  retrograde  motion. 

XI.  The  Caufcs  which  induce  the  Retrograde  Motions  of 

animal  V cjfels,  and  the  Aledicines  by  which  the  natural 

Motions  are  rejlored. 

1.  Such  is  the  conftruAion  of  animal  bodies,  that  all  their 
parts,  which  are  fubjeAed  to  lets  ftimuli  than  nature  dctigned, 
perform  their  funAions  with  lefs  accuracy : thus,  when  too 
watery  or  too  acefcent  food  is  taken  into  die  ftomach,  indigel- 
tion,  and  flatulency,  and  heartburn  fucceed. 

2.  Another  law  of  irritation,  connate  with  our  exiftence, 
is,  that  all  thofe  parts  of  the  body  which  have  previouflv  been 
expofed  to  too  great  a quantity  of  fuch  ftimuli  as  ftrongjy  af- 
fedt  them,  become  for  iome  time  afterwards  difobedient  to  the 
natural  quantity  of  their  adapted  ftimuli. — Thus  the  eye  is  in- 
capable of  feeing  objeAs  in  an  obfcure  room,  though  the  iris 
is  qui  e dilated,  after  having  been  expofed  to  the  meridian  iun. 

3.  There  is  a third  law  of  irritation,  that  all  the  parts  of 
our  bodies,  which  have  been  lately  fubjeAed  to  lefs  ft  Until  us 
than  they  have  been  accuftomed  to  when  they  are  expofed  to 
their  ufual  quantity  of  ftimu’us,  are  excited  into  more  energe- 
tic motions : thus,  when  we  come  from  a duftcy  cavern  into  the 
glare  of  day-light,  our  eves  are  dazzled;  and  after  emerging 
from  the  cold  bath,  the  fkin  becomes  warm  and  red. 

There  is  a fourth  law  of  irritation,  that  all  the  parts  of  our 
bodies,  which  are  fubjeAed  to  ftili  ftrenger  ftimuli  tor  a length 
of  time,  become  torpid,  and  refuie  to  obey  even  thele  fironger 
ftimuli;  and  thence  do  their  offices  very  imperfeftlv. — Thus. 

if 


Sect.XXIX.ii,.  RETROGRADE  ABSORBENTS.  253 

jf  any  one  looks  earneftly  for  fome  minutes  on  an  area,  an 
inch  diameter,  of  red  fdk,  placed  on  a fheet  of  white  paper, 
the  image  of  the  fdk  will  gradually  become  pale,  and  at 
length  totally  vanifh. 

5.  Nor  is  it  the  nerves  of  fenfe  alone,  as  the  optic  and  audi- 
tory nerves,  that  thus  become  torpid  when  the  dim  ulus  is  with- 
drawn, or  their  irritability  decreafed ; but  the  motive  mufcles, 
when  they  are  deprived  of  their  natural  ftimuli,  or  of  their  irri- 
tability, become  torpid  and  paralytic  ; as  is  feen  in  the  tremu- 
lous hand  of  a drunkard  in  the  morning,  and  in  the  awkward 
ftep  of  age. 

The  hollow’  mufcles  alfo,  of  which  the  various  veffels  of  the 
body  are  contracted,  when  they  are  deprived  of  their  natural 
ftimuJi,  or  of  their  due  degree  of  irritability,  not  only  become 
tremulous  as  the  arterial  pulfations  of  dying  people,  but  alfo 
frequently  invert  their  motions,  as  in  vomiting,  in  hyfteric  fuf- 
focations,  and  diabetes  above  defcribed. 

I mud  beg  your  patient  attention,  for  a few’ moments,  whiift 
I endeavour  to  explain,  how  the  retrograde  actions  of  our 
hollow  mufcles  are  the  confeqpence  of  their  debility;  as  the 
tremulous  actions  of  the  folid  mufcles  are  the  confequence  of 
their  debility.  When,  through  fatigue,  a mufcle  can  acf  no 
longer,  the  antagonifl  mufcles,  either  by  their  inanimate  elaf- 
ticity,  or  by  their  animal  adtion,  draw  the  limb  into  a contrary 
direction : in  the  folid  mufcles,  as  thoie  of  locomotion,  their 
adtions  are  afTociated  in  tribes,  which  have  been  accuftomed 
to  fynchronous  adtion  only ; hence,  when  they  are  fatigued, 
only  a lingle  contrary  effort  takes  place;  which  is  either  tre- 
mulous, when  the  fatigued  mufcles  are  again  immediately 
brought  into  adtion  ; or  it  is  a pendiculation,  or  firetching, 
where  they  are  not  immediately  again  brought  into  adtion. 

Now,  the  motions  of  the  hollow  mufcles,  as  they  in  general 
propel  a fluid  along  their  cavities,  are  afTociated  intrains,  which 
have  been  accultomed  to  lucceffive  actions ; hence,  w’hen  one 
ring  of  fuch  a mufcle  is  fatigued  from  its  too  great  debility,  and 
is  brought  into  retrograde  adtion,  the  next  ring  from  its  affo- 
ciation  falls  fucceflivdy  into  retrograde  adtion ; and  fo  on 
throughout  the  whole  canal.  See  Sedt.  XXV.  6. 

6.  But  as  the  retrograde  motions  of  the  ftomach,  oefopha- 
gus,  and  fauces  in  vomiting,  are,  as  it  w’ere,  apparent  to  the 
eye,  we  thall  conlider  this  operation  more  minutely,  that  the 
fimilar  operations  in  the  more  recondite  parts  of  our  lyftem 
may  be  eafier  underftood. 

From  certain  naufeous  ideas  of  the  mind,  from  an  uncrate- 
ful  tafte  in  the  mouth,  or  from  foetid  imefls,  vomiting  is  fome- 

times 


RETROGRADE  ABSORBENTS.  Sect.XXIX.ii, 

times  inftantly  excited ; or  even  from  a Broke  on  the  head ; 
or  from  the  vibratory  motions  of  a fhip ; all  which  originate 
from  affociation,  or  lympathy.  See  Sedf.  XX.  on  Vertigo. 

But  when  the  ftomach  is  fubjecied  to  a lefs  ftimulus  than  is 
natural,  according  to  the  ftrft  law  of  irritation  mentioned  above, 
its  motions  become  diffcurbed,  as  in  hunger;  firft,  pain  is  pro- 
duced, then  ficknefs,  and,  at  length,  vain  efforts  to  vomit,  as 
many  authois  inform  us. 

But  when  a great  quantity  of  wine,  or  of  opium,  is  fwal- 
lowed,  the  retrograde  motions  of  the  ftomach  do  not  occur  till 
after  feveral  minutes,  or  even  hours ; for  when  the  power  of 
fo  ftrong  a ftimulus  ceafes,  according  to  the  fecond  law  of  ir- 
ritation, mentioned  above,  the  periftaltic  motions  become  tre- 
mulous, and  at  length  retrograde;  as  is  well  known  to  the 
drunkard,  who.  on  the  next  morning,  has  ficknefs  and  vomitings. 

When  a Bill  greater  quantity  of  w ine,  or  of  opium,  or  w hen 
naufeous  vegetables,  or  ftrong  bitters,  or  metallic  falts,  are 
taken  into  the  ftomach,  they  quickly  induce  vomiting ; though 
all  thefe,  in  lefs  dotes,  excite  the  ftomach  into  more  energetic 
adfion,  and  ftrengthen  the  digeftion  ; as  the  flowers  of  cha- 
momile, and  the  vitriol  of  zine:  for,  according  to  the  fourth 
law  of  irritation,  the  ftomach  will  not  long  be  obedient  to  a 
ftimulus  fo  much  greater  than  is  natural;  but  its  adfion  be- 
comes firft  tremulous,  and  then  retrograde. 

7.  When  the  motions  of  any  veffels  become  retrograde,  lefs 
heat  of  the  body  is  produced;  for  in  paroxyfms  of  vomiting,  of 
hyfteric  affections,  of  diabetes,  of  afthma,  the  extremities  of 
the  body  are  cold:  hence  we  may  conclude,  that  thefe  fymptoms 
arife  from  the  debility  of  the  parts  in  adlion  ; for  an  increafe  of 
mufcular  acftion  is  always  attended  with  increafe  of  heat. 

8.  But  as  animal  debility  is  owing  to  defedt  of  ftimulus,  or 
to  defeat  of  irritability,  as  fhewn  above,  the  method  of  cure 
is  eafily  deduced : when  the  vafcular  mufcles  are  not  excited 
into  their  due  adlion  by  the  natural  ftimuli,  we  fhould  exhibit 
thofe  medicines  wdiich  poflefs  a ftill  greater  degree  of  ftimu- 
lus ; amongft  thefe  are  the  foetids,  the  volatiles,  aromatics, 
bitters,  metallic  falts,  opiates,  wine,  which  indeed  fhould  be 
given  in  ftnall  dofes,  and  frequently  repeated.  To  thefe  fhould 
be  added  conftant,  but  moderate  exercife,  cheerfulnefs  of  mind, 
and  change  of  country  to  a warmer  climate;  and  perhaps  oc- 
cafionally  the  external  ftimulus  of  blifters. 

It  is  alfo  frequently  ul'eful  to  diminifh  the  quantity  of  natural 
ftimulus  for  a lhort  time,  by  which  afterwards  the  irritability 
of  the  fyftem  becomes  increafed,  according  to  the  third  law  of 
irritation  above-mentioned.  Hence  the  ufe  of  baths  fomewhat 
bolder  than  animal  heat,  and  of  equitation  in  the  open  air. 


Sect. XXX.  i.  PARALYSIS  OF  THE  LIVER.  25$ 


The  catalogue  of  difeafes,  owing  to  the  retrograde  motions  of 
lymphatics , is  here  omitted , as  it  will  appear  in  the  fecond 
volume  of  this  work.  The  following  is  the  conclufion  to 
this  thefs  of  Mr.  Charles  Darwin. 

Thus  have  I endeavoured,  in  a concife  manner,  to  explain 
the  numerous  difeafes  which  deduce  their  origin  from  the  invert- 
ed motions  of  tne  hollow  mufcles  of  our  bodies : and  it  is  pro- 
bable, that  Saint  Vitus’s  dance,  and  the  hammering  of  fpeech, 
originate  from  a fimiiar  inverted  order  of  the  affociated  mo- 
tions of  fome  of  the  folid  mufcles,  which,  as  it  is  foreign  to  my 
prefent  purpofe,  I fhall  not  here  difeufs. 

I beg,  iliullrious  profeilors,  and  ingenious  fellow-ftudents, 
that  vou  will  recoiled!  how  difficult  a tafk  I have  attempted, 
to  evince  the  retrograde  motions  of  the  lymphatic  vedels,  when 
the  velfels  themfelves,  for  fo  many  ages,  efcaped  the  eyes  and 
glades  of  philofophers : and  if  you  are  not  yet  convinced  of 
the  truth  of  this  theory,  hold,  I entreat  you,  your  minds  in 
fufpence,  till  Anatomy  draws  her  fword  with  happier  omens, 
cuts  afunder  the  knots  which  entangle  Physiology;  and, 
like  an  augur,  infpecling  the  immolated  vidlim,  announces  to 
-mankind  the  wifdom  of  HEAVEN, 


SECT.  XXX. 

PARALYSIS  OF  THE  LIVER  AND  KIDNEYS. 

1.  I.  Bile-duffs  lefs  irritable  after  having  been  fimulated 
much.  2.  Jaundice  from  paralyfs  of  the  bile-duffs  cured 
by  elcffric  Jhocks.  3.  From  bile-Jiones.  Experiments  on 
bile-fones.  Oil-vomit.  4.  Pal/y  of  the  liver , two  cafes. 
5.  Schirrofty  of  the  liver.  6.  Large  livers  of  geefe.  II. 
Paralyfs  of  the  kidneys.  III.  Story  of  Prometheus. 

I.  1.  FROM  the  ingurgitation  of  fpirituous  liquors  into  the 
ftomach  and  duodenum,  the  termination  of  the  common  bile- 
dud!  in  that  bowel  becomes  flimulated  into  unnatural  adlion, 
and  a greater  quantity  of  bile  is  produced  from  all  the  fecretory 
vedels  of  the  liver,  by  the  affociation  of  their  motions  with 
thofe  of  their  excretory  dud!s;  as  has  been  explained  in  Sec- 
tion XXIV.  and  XXV.  but  as  all  parts  of  the  body  that  have 
been  affedled  with  ftronger  ftimuli  for  any  length  of  time,  be- 
come lefs  fufceptible  of  motion,  from  their  natural  weaker  fti- 
■mub,  it  follows,  that  the  motions  of  the  fecretory  vedels,  and 
in  confequence  the  fecretion  of  bile,  is  lefs  than  is  natural  dur- 
ing the  intervals  of  fobriety.  2.  If  dais  ingurgitation  of  fpiri- 
tuous 


2.56  PARALYSIS  OF  THE  LIVER.  Sect.  XXX.  1. 

tuous  liquors  has  been  daily  continued  in  confiderable  quanti- 
ty, and  is  then  fuddenly  intermitted,  a languor  or  paralvlis  of 
the  common  bile-du6t  is  induced ; the  bile  is  prevented  from 
being  poured  into  the  inteftines;  and  as  the  bilious  abforbeuts 
are  ftimulated  into  ftronger  adtion  by  its  accumulation,  and  by 
the  acrimony  or  vifcidity  which  it  acquires  by  delay,  it  is  ab- 
forbed,  and  carried  to  the  receptacle  of  the  chyle;  or  other- 
wife  the  fecretory  veffels  of  the  liver,  by  the  above-mentioned 
ftimulus,  invert  their  motions,  and  regurgitate  their  contents 
into  the  blood,  as  fometimes  happens  to  the  tears  in  the  lach;y- 
mal  fack,  fee  Se£t.  XXIV.  2.  7.  and  one  kind  of  jaundice  is 
brought  on. 

There  is  reafon  to  believe,  that  the  bile  is  mod  frequently 
returned  into  the  circulation  by  the  inverted  motions  of  tiiefe 
hepatic  glands,  for  the  bile  does  not  feem  liable  to  be  abforbcd 
by  the  lymphatics,  for  it  foaks  through  the  gall-dudf?,  and  is 
frequently  found  in  the  cellular  membrane.  1 his  kind  is  jaun- 
dice, is  not  generally  attended  with  pain,  neither  at  the  extre- 
mity of  bile-du£t,  where  it  enters  the  duodenum,  nor  on  the 
region  of  the  gall-bladder. 

Mr.  S.  a gentleman  between  40  and  50  years  *of  age,  had 
had  the  jaundice  about  lix  weeks,  without  pain,  ficknefs,  or 
fever;  and  had  taken  emetics,  cathartics,  mercurials,  bitters, 
chalybeates,  eflential  oil,  and  aether,  without  apparent  advan- 
tage. On  a iuppofition  that  the  obftrudfion  ot  the  bile  might 
be  owing  to  the  paralyfis,  or  torpid  adtion  of  the  common  1 
bile-dudf,  and  the  ffimulants  taken  into  the  llomach  feeming 
to  have  no  effect,  I diredled  half  a fcore  fmart  electric  {hocks, 
from  a coated  bottle,  which  held  about  a quart,  to  be  pafl'ed 
through  the  liver,  and  along  the  courfe  of  the  common  gall- 
du6f,  as  near  as  could  be  guefleJ,  and  on  that  very  day  the 
Pools  became  yellow ; he  continued  the  eledtric  fhocks  a few 
days  more,  and  his  {kin  gradually  became  clear. 

3.  The  bilious  vomiting  and  purging  that  aifedls  fome  peo- 
ple by  intervals  of  a few  weeks,  is  a lels  degree  of  this  difeafe  : 
the  bile-dudt  is  lefs  irritable  than  natural ; and  hence  the  bile 
becomes  accumulated  in  the  gall-bladder  and  hepatic-dudbs,  till 
by  its  quantity,  acrimony,  or  vifcidity,  a greater  degree  of  irrita- 
tion is  produced,  and  it  is  fuddenly  evacuated ; or,  laftly,  hom 
the  abforption  of  the  more  liquid  parts  of  the  bile,  the  remainder 
becomes  infpifiated,  and  chrvftallizcs  into  mafles  too  large  to 
pafs,  and  forms  another  kind  of  jaundice,  where  the  bile-dudi:  is 
not  quite  paralytic,  or  has  regained  its  irritability. 

This  difeafe  is  attended  with  much  pain,  which  at  hrft  is  felt 
at  the  pit  of  the  ftomach,  exadtly  in  the  center  ot  the  body, 

where 


Sect.  XXX.  i.  PARALYSIS  OF  THE  LIVER.  257 

where  the  bile-duff  enters  the  duodenum : afterwards,  when  the 
lize  of  the  bile-ftones  increafe,  it  is  alfo  felt  on  the  right  lide, 
where  the  gall-bladder  is  htuated.  The  former  pain  at  the  pit 
of  the  ftomach  recurs  by  intervals,  as  the  bile-ftone  is  pufhed 
againfl:  the  neck  of  the  dudf ; like  the  paroxyfms  of  the  ftone  in 
the  urinary  bladder,  the  other  is  a more  dull  and  conflant  pain. 

Where  thefe  bile-flones  are  too  large  to  pafs,  and  the  bile- 
ducts  poffefs  their  fenfibility,  this  becomes  a very  painful  and 
hopdefs  difeafe.  I made  the  following  experiments  with  a 
view  to  their  chemical  folution. 

Some  fragments  of  the  fame  bile-hone  were  put  into  the 
weak  lpirit  of  marine  fait,  which  is  fold  in  the  drops,  and  into 
a folution  of  mild  alcali,  and  into  a lolution  of  cauhic  alcali,  and 
into  oil  of  turpentine,  without  their  being  diffolved.  All  thefe 
mixtures  were,  after  fome  time,  put  into  a heat  ol  boiling  water, 
and  then  the  oil  of  turpentine  diffolved  its  fragments  of  bile- 
hone;  but  no  alteration  was  produced  upon  thofe  in  the  other- 
liquids,  except  fome  change  of  their  colour. 

Some  fragments  of  the  fame  bile-hone  were  put  into  vitriolic 
tether,  and  were  quickly  diffolved  without  additional  heat. 
Might  not  aether,  mixed  with  yolk  of  egg,  or  with  honey,  be 
given advantageouhy  in  bilious  concretions? 

I have,  in  two  inhances,  feen  from  thirty  to  fifty  bile-hones 
come  away  by  hool,  about  the  fize  of  large  peafe,  after  having 
given  fix  grains  of  calomel  in  the  evening,  and  four  ounces  of 
oil  of  almonds  or  olives  on  the  iucceeding  morning.  I have  alfo 
given  half  a pint  of  good  olive  or  almond  oil,  as  an  emetic,  dur- 
ing the  painful  fit,  and  repeated  it  in  half  an  hour,  if  the  firh 
did  not  operate,  with  frequent  good  effect. 

4.  Another  difeafe  of  the  liver,  which  I have  feveral  times 
obferved,  confihs  in  the  inability,  or  paralvfis  of  the  fecretory 
veffels.  This  difeafe  has  generally  the  fame  caufe  as  the  pre- 
ceding one, — the  too  frequent  potation  of  fpirituous  liquors,  or 
the  too  hidden  omiffion  of  them  after  the  habit  is  confined ; and 
is  greater  or  lei's,  in  proportion  as  the  whole  or  a part  of  the 
liver  is  affedted,  and  as  the  inability  or  paralyiis  is  more  or 
lefs  complete. 

This  palfy  of  the  liver  is  known  from  thefe  fymptoms : The 
patients  have  generally  paffed  the  meridian  of  life,  have  drank 
fermented  liquors  daily,  but  perhaps  not  been  opprobrious 
drunkards;  thev  lofe  their  appetite,  then  their  fleih  and  ftrength 
diminifh  in  coniequence ; there  appears  no  bile  in  their  ftools, 
nor  in  their  urine ; nor  is  any  hardnefs  or  fwelling  perceptible  on 
the  region  of  the  liver.  But  what  is  peculiar  to  this  difeafe,  and 
diftinguiihes  it  from  all  others  at  the  firft  glance  of  the  eye,  is 


253  PARALYSIS  OF  THE  LIVER.  Sect.  XXX.  t. 

the  bombycinous  colour  of  the  fkin,  which,  like  that  of  full- 
grown  filk-worms,  has  a degree  of  tranfparency,  with  a yellow 
tint,  not  greater  than  is  natural  to  the  ferum  of  the  blood. 

Mr.  C.  and  Mr.  B.  both  very  ftrcng  men.  between  fifty  and 
fixty  years  of  age,  who  had  drank  ale  at  their  meals  inftead  of 
fmall  beer,  but  were  not  reputed  hard-drinkers,  fuddenly  became 
weak,  loft  their  appetite,  ftefh  and  ftrength,  with  all  ihe  fynap- 
toms  above  enumerated,  and  died  in  about  two  months  from 
the  beginning  of  their  malady.  Mr.  C.  became  anafarcous  a 
few  days  before  his  death ; and  Mr.  B.  had  frequent  and  great 
haemorrhages  from  an  iflue,  and  fome  parts  of  his  mouth,  a few 
days  before  his  death.  In  both  thefe  cales  calomel,  bitters  and 
chalybeates  were  repeatedly  ufed  without  effedl. 

One  of  the  patients  delcribed  above,  Mr.  C.  was  by  trade 
a plumber ; both  of  them  could  digeft  no  food,  and  died  appa- 
rently for  want  of  blood.  Might  not  the  transfufton  of  blood 
be  ufed  in  thefe  cafes  with  advantage? 

5.  When  the  paralyfis  of  the  hepatic  glands  is  lefs  complete, 
or  lefs  univerfal,  a fchirroftty  of  fome  part  of  the  liver  is  induced  - 
for  the  fecretory  veflels,  retaining  fome  of  their  living  power, 
take  up  a fluid  from  the  circulation,  without  being  fufficiently 
irritable  to  carry  it  forwards  to  their  excretory  du£Is ; hence  the 
body,  or  receptacle  of  each  gland,  becomes  inflated ; and  this 
diftention  increafes,  till,  by  its  very  great  ftimulus,  inflammation 
is  produced,  or  till  thofe  parts  of  the  vifcus  become  totally  pa- 
ralytic. This  difeafe  is  diftinguifhable  from  the  ioregoing  by 
the  palpable  hardnefs  or  largenefs  of  the  liver ; and  as  the  hepa- 
tic glands  are  not  totally  paralytic,  or  the  whole  liver  net  af- 
fedted,  fome  bile  continues  to  be  made.  The  inflammations  of 
this  vifcus,  conl'equent  to  the  fchirroftty  of  it,  belong  to  the  dif- 
eafes  of  die  fenfttive  motions,  and  will  be  treated  of  hereafter. 

6.  The  ancients  are  faid  to  have  poflefled  an  art  of  increafing 
the  livers  of  geefe  to  a lize  greater  than  the  remainder  of  the 
goofe.  Martial.  1.  13.  epig.  58.  This  is  faid  o have  been  done 
by  fat  and  figs.  Horace,  1.  2.  fat.  8. — Juvenal  lets  thefe  large 
livers  before  an  epicure  as  a great  rarity.  Sat.  5.  1.  1 1 4 ; and 
Perfius,  fat.  6.T.  71.  Pliny  fays  thefe  large  goofe-livers  were 
foaked  in  mulled  milk,  that  is,  I luppole,  milk  mixed  with  honey 
and  wine;  and  adds,  “that  it  is  uncertain  whether  Scipio  Me- 
teilus,  of  confular  dignity,  orM.  Seftius,  a Roman  knight,  was 
the  great  difeoverer  of  this  excellent  dilli.”  A modem  travel- 
ler, I believe  Mr.  Brydone,  afterts  that  the  art  of  enlarging 
the  livers  of  geefe  ftill  exifts  in  Sicily ; and  it  is  to  be  lament- 
ed that  he  did  not  import  it  into  his  native  country,  as  iome 
method  of  affcdling  the  human  liver  might,  perhaps,  have  been 

colledPtl 


SfecT.  XXX.  2, 3.  PARALYSIS  OF  THE  LIVER.  25$ 

colledfed  from  it;  befides,  the  honour  he  might  have  acquired 
in  improving  our  giblet  pies. 

Our  wifer  caupones,  I am  told,  know  how  to  fatten  their 
fowls,  as  well  as  their  geefe,  for  the  London  markets,  by 
mixing  gin  inftead  of  figs  and  fat  with  their  food ; by  which 
they  are  laid  to  become  lleepy,  and  to  fatten  apace,  and  pro- 
bably acquire  enlarged  livers,  as  the  fwine  are  alferted  to  do, 
which  are  fed  on  fine  fediments  of  barrels  in  the  diftilleries;  and 
which  fo  frequently  obtains  in  thofe  who  ingurgitate  much 
ale,  or  wine,  or  drams. 

II.  The  irritative  difeafes  of  the  kidneys,  pancreas,  fpleen, 
and  other-  glands,  are  analogous  to  thofe  of  the  liver  above 
defcribed,  differing  only  .in  the  confequences  attending  their  in- 
ability to  a£tion.  For  inftance,  when  the  fecretory  veffels  of 
the  kidneys  become  difobedient  to  the  ftimulus  of  the  palling 
current  of  blood,  no  urine  is  feparated  or  produced  by  them ; 
their  excretory  mouths  become  filled  with  concreted  mucus,  or 
calculus  matter,  and  in  eight  or  ten  days  ftupor,  and  death  fu- 
pervenes  inconfequence  the  retention  of  the  feculent  part  of 
the  bloods 

This  difeafe,  in  a Fighter  degree,  or  when  only  a part  of  the 
kidney  is  affected,  is  fucceeded  by  partial  inflammation  of  the 
kidney,  in  confequence  of  previous  torpor.  In  that  cafe, 
greater  actions  of  the  fecretory  veffels  occur,  and  the  nucleus 
of  gravel  is  formed  by  the  inflamed  mucous  membranes  of  the 
tubuli  uriniferi,  as  farther  explained  in  its  place. 

This  torpor,  or  paralyfis  of  the  fecretory  veffels  of  the  kid- 
neys, like  that  ol  the  liver,  owes  its  origin  to  their  being  pre- 
vipufly  habituated  to  too  great  ftimulus;  which,  in  this  coun- 
try, is  generally  owing  to  the  alcohol  contained  in  ale  or  wine; 
and  hence  muff  be  regiftered  amongft  the  dileafes  owing  to  in- 
ebriety; though  it  may  be  caufed  by  whatever  occaftonally  in- 
flames the  kidney ; as  too  violent  riding  on  horleback,  or  the  cold 
from  a damp  bed,  or  by  fieeping  011  the  cold  ground  or  per- 
haps by  drinking  in  general  too  little  aqueous  fluids. 

III.  I ftiall  conclude  this  fection  on  the  difeafes  of  the  liver 
induced  by  ipirituous  liquors,  with  the  well  known  ftory  of 
Prometheus,  which  ieems  indeed  to  have  been  invented  by  phy- 
ficians  in  thofe  ancient  times,  when  all  things  weie  clothed  in 
hieroglyphic,  or  in  fable..  Prometheus  was  painted  as  healing 
fire  from  heaven,  which  might  well  reprelent  the  inflammable 
fpirit  produced  by  fermentation,  which  may  be  fa  id  to  animate 
or  enliven  the  man  of  clay : whence  the  conquefts  ol  Bacchus, 
as  well  as  the  temporary  mirth  and  noife  of  his  devotees.  But 
the  after  punifhment  of  thofe  who  fteal  this  accurfed  fire,  is  a 

M m vulture. 


OF  TEMPERAMENTS. 


Sect.  XXXI. 


260 

Vulture  gnawing  the  liver ; and  well  allegorifes  the  poor  inebri- 
ate lingering  for  years  under  painful  hepatic  difeafes.  When 
the  expediency  of  laying  a further  tax  on  the  diftillation  of 
fpirituous  liquors  from  grain  was  canvaffed  before  the  Houfe 
of  Commons  fome  years  ago,  it  was  faid  of  the  diftillers,  with 
great  truth,  “ They  take  the  bread from  the  people,  and  con- 
vert it  into  poifsn  /”  Y et  is  this  manufactory  of  difeale  per- 
mitted to  continue,  as  appears  by  its  paying  into  the  trealury 
above  900,0001.  near  a million  ot  money  annually.  And  thus, 
under  the  names  of  rum,  brandy,  gin,  whifky,  ulqucbaugh, 
wine,  cyder,  beer,  and  porter,  alcohol  is  become  the  bane  of 
the  Chriftian  woild,  as  opium  of  the  Mahometan. 

Evoe ! parce,  liber? 

■ v Parce,  gravi  metuende  thirso ! Hor. 


SECT.  XXXI. 

OF  TEMPERAMENTS. 

t.  The  temperament  of  dccrcafed  irritability  known  by  weak 
pul/e,  large  pupils  of  the  eyes,  cold  extremities.  Are  gene- 
rally fuppofed  to  be  too  irritable.  Bear  pain  better  than 
labour.  Natives  of  N orth- America  contrafed  with  thoje  • 
upon  the  coajl  of  Africa.  Narrow  and  broad-Jhouldered J 
people.  Irritable  confutations  bear  labour  better  than 
pain.  II.  Temperament  of  increafed  fenfibility.  Liable 
to  intoxication,  to  inflammation , haemoptoc,  gutta  ferena, 
enthufiafn , delirium , reverie:  Thefe  conflitutions  are  in- 

dolent to  voluntary  exertions,  and  dull  to  irritations.  The 
natives  of  South- America  and  brute  animals  of  this  tem- 
perament. III.  Of  increafed  voluntarily  : thefe  are  fub- 
jeft  to  locked  jaw,  convulflons , epilepfy , mania.  Are  very 
adtive\  bear  cold,  hunger,  fatigue.  Are  fuited  to  great 
exertions.  This  temperament  diflinguiflies  mankind  from 
other  animals.  IV.  Of  increafed  affociation.  Thefe  have 
great  memories , arc  liable  to  quarian  agues,  and  flronger 
fympathies  of  parts  with  each  other.  V.  Change  of  tem- 
peraments into  one  another . 


ANCIENT  writers  have  fpoken  much  of  temperaments, 
but  without  fufficient  precifion.  By  temperament  of  the  iyftem 
fliould  be  meant  a permanent  predifpohtion  to  certain  clafles  of 
difeales:  without  this  definition  a temporary  predifpofition  to 
every  diftinCt  malady  might  be  termed  a temperament.  There 
are  four  kinds  of  conftitution,  which  permanently  deviate  from 


Sect.  XXXI.  i.  OF  TEMPERAMENTS.  261 

good  health,  and  are  perhaps  fufficiently  marked  to  be  diftin- 
gui fired  from  each  other,  and  conftitute  the  temperaments  or 
-predifpofitions  to  the  irritative,  fenfitive,  voluntary,  and  aflo- 
;ciate  clafles  of  difeafes. 

T.  The  Temperament  of  d-ecreafed  Irritability. 

The  difeafes,  which  are  caufed  by  irritation,  mu  ft  frequently 
•originate  from  the  defect  of  it ; for  thole  which  are  immediately 
•owing  to  the  excefs  of  it,  as  the  hot  fits  of  fever,  are  generally 
occalioned  by  an  accumulation  of  fenforial  power,  in  confe- 
quence  of  a previous  defedl  of  irritation,  as  in  the  preceding 
cold  tits  of  fever.  Whereas  the  difeafes  which  are  caufed  by 
fenfation  and  volition,  mult  frequently  originate  from  the  ex- 
cefs of  thofe  fenforial  powers,  as  will  be  explained  below. 

The  temperament  of  decreafed  irritability  appears  from  the 
following  circurnftances,  which  fhew,  that  the  mufcular  fibres 
or  organs  of  fenfe  are  liable  to  become  torpid  or  quiefcent,  from 
lefs  defedt  of  {Emulation  than  is  productive  of  torpor  or  quie- 
scence in  other  conftitutions. 

1.  The  firft  is  the  weak  puife,  which,  in  fome  conftitu- 
tions, is,  at  the  fame  time,  quick.  2.  The  next  moft  marked 
•criterion  of  this  temperament  is  the  largenefs  of  the  aperture 
of  the  iris,  or  pupil  of  the  eve,  which  has  been  reckoned  by 
fome  a beautiful  feature  in  the  female  countenance,  as  an  in- 
dication of  delicacy;  but  to  an  experienced  obferver,  it  is  an 
indication  of  debility,  and  is  therefore  a defedf,  not  an  excel- 
lence. The  third  moft  marked  circumftance  in  this  conftitu- 
tion  is,  that  the  extremities,  as  the  hands  and  feet,  or  nofe  and 
ears,  are  liable  to  become  cold  and  pale  in  fituations  in  refpect 
to  warmth,  where  thofe  of  greater  ftrength  are  not  afifedted. 
Thofe  of  this  temperament  are  lubjedl  to  hyfteric  affections, 
nervous  fevers,  hydrocephalus,  fcrophula,  and  conl'umption,  and 
to  all  other  difeafes  of  debility. 

Thofe  who  poffefs  this  kind  of  conftitution  are  popularly 
Xuppofed  to  be  more  irritable  than  is  natural,  but  are  in  reality 
lefs  fo.  This  rniftake  has  arifen  from  their  generally  having 
a greater  quicknefs  of  puife,  as  explained  in  Sedt.  XII.  1.  4. 
XII.  3.  3. ; but  this  frequency  of  puife  is  not  neceftary  to  the 
temperament,  like  the  debility  of  it. 

Perfons  of  this  temperament  are  frequently  found  amongft 
the  fofter  fex,  and  amongft  narrow-fhouldered  men,  who  are 
Xaid  to  bear  labour  worfe,  and  pain  better  than  others.  This 
laft  circumftance  is  fuppofed  to  have  prevented  the  natives 
of  North- America  from  having  been  made  Haves  of  by  the 
Europeans.  They  are  a narrow-fhouldered  race  of  people, 

and 


262  OF  TEMPERAMENTS.  Sect.  XXXI.  2. 

one!  will  rather  expire  under  the  lath,  than  he  made  to  ]r  - 
hour.  Some  nations  of  Aha  have  fmall  hands,  as  mav  he 
feen  by  the  handles  of  their  fcvmetars  ; which,  with  their  nar- 
row moulders,  (hew,  that  they  have  not  been  accuftomed  to  fo 
great  labour  with  their  hands  and  arms,  as  the  European  na- 
tions in  agriculture,  and  thofe  on  the  coafts  of  Africa  in  fwim- 
rning  and  rowing.  Dr.  Maningham,  a popular  accoucheur, 
in  the  beginning  of  this  century,  obferves  in  his  Aporifms,  that 
broad-ihouidered  men  procreate  broad-fhouldered  children. 
Now,  as  labour  ftrengthens  the  muicles  employed,  and  in- 
creates  their  bulk,  it  would  feem  that  a few  generations  of  la- 
bour or  of  indolence,  may,  in  this  refpedl,  change  the  form 
and  temperament  ot  the  body. 

On  the  contrary,  thofe  who  are  happily  poflefied  of  a great 
degree  of  irritability,  bear  labour  better  than  pain,  and  are  ftrong, 
adlive,  and  ingenious.  But  there  is  not  properly  a temperament 
ot  increafed  irritability  tending  to  difeale,  becauie  an  increafed 
quantity  of  irritative  motions  generally  induces  an  increafe  of 
plealure  or  pain,  as  in  intoxication,  or  inflammation  ; and  then 
the  new  motions  are  the  immediate  conlequences  ot  increafed 
fenfation,  not  of  increafed  irritation ; which  have  hence  been 
to  perpetually  confounded  with  each  other. 

IT.  Temperament  of  Senjibil'ily. 

There  is  not  properly  a temperament  or  predifpofition,  to 
difeafe,  from  decreafed  fenfibility,  ftnee  irritabilitv  and  not  ien- 
tlbility  is  immediately  neceiTary  to  bodily  health.  Hence  it  is  the 
excefs  ot  fenfation  atone,  as  it  is  the  detedf  of  irritation,  that 
mofl  frequently  produces  difeafe.  This  temperament  ot  increaf- 
ed fenfibility  is  known  from  the  increafed  activity  ot  all  thofe 
motions  ot  the  organs  of  fenfe  and  muicles,  which  are  exert- 
ed in  confequence  of  pleafure  or  pain,  as  in  the  beginning  ot 
drunkennefs,  and  in  inflammatory  lever.  Hence  thoie  ot  this 
constitution  are  liable  to  inflammatory  difeafes,  as  hepatitis , 
and  to  that  kind  of  confumption  which  is  hereditary,  and  com- 
mences with  flight  repeated  hoemoptoe.  They  have  high-co- 
loured lips,  frequently  dark  hair  and  dark  eyes,  with  large  pu- 
pils, and  are  in  that  cafe  iubjeift  to  gutta  ferena.  They  ire 
liable  to  enthufiafm,  delirium,  and  reverie.  In  this  laft  cir- 
cuinftance  they  are  liable  to  ftart  at  the  clapping  of  a door; 
becaufe  tire  more  intent  any  one  is  on  the  pafling  current  ot  his 
ideas,  the  greater  lurprife  he  experiences  on  their  being  di {fe- 
vered bv  tome  external  violence,  as  explained  in  Seift.  XIX. 
on  Rcyerie. 


Sect.  XXXI.  3.  OF  TEMPERAMENTS.  263 

As  in  thefe  conflitutions  more  than  the  natural  quantities  of 
fenfitive  motions  are  produced  by  the  increafed  quantity  of  fen- 
fation  exifting  in  the  habit,  it  follows,  that  the  irritative  mo- 
tions will  be  performed  in  fome  degree  with  lefs  energy,  ow- 
ing to  the  great  expenditure  of  fenforial  power  on  the  fenfitive 
ones.  Hence  thofe  of  this  temperament  do  not  attend  to  flight 
Simulations,  as  explained  in  Serif.  XIX.  But  when  a ftimulus 
is  fo  great  as  to  excite  fenfation,  it  produces  greater  fenfitive 
arifionsofthe  l'yftem  than  in  others;  fuch  as  delirium  or  inflam- 
mation. Hence  they  are  liable  to  be  abfent  in  company;  fit 
or  lie  long  in  one  pofrure ; and  in  winter  have  the  fkin  of 
their  legs  burnt  into  various  colours  by  the  fire.  Hence  alfo 
they  are  fearful  of  pain ; covet  mufic  and  fleep ; and  delight  in 
poetrv  and  romance. 

As  the  motions  in  confequenee  of  fenfation  are  more  than 
natural,  it  alfo  happens,  from  the  greater  expenditure  of  fenfo- 
rial power  on  them  that  the  voluntary  motions  are  lefs  eafily 
exerted.  Hence  thefubjerils  of  this  temperament  are  indolent 
in  refperit  to  all  voluntary  exertions,  whether  of  mind  or  body. 

A race  of  people  of  this  defcription  feems  to  have  been 
found  by  the  Spaniards  in  the  ifiands  of  America,  where  they 
firfl:  landed,  ten  of  whom  are  faid  not  to  have  coniumed  more 
food  than  one  Spaniard,  nor  to  have  been  capable  of  more  than 
one  tenth  of  the  exertion  of  a Spaniard.  Robertfon’s  Hiftory. 
In  a ftate  fimilar  to  this  the  greateff  part  of  the  animal  world 
pafs  their  lives,  between  fleep  or  inarifive  reverie,  except  when 
they  are  excited  by  the  call  of  hunger. 

Tir.  The  Temperament  of  Increafed  Voluntarily. 

Thofe  of  this  conftitution  differ  from  both  the  laft  mentioned 
In  this,  that  the  pain,  which  gradually  fubfides  in  the  firfl,  and 
is  productive  of  inflammation  or  delirium  in  the  fecond,  is  in 
this  fucceeded  by  the  exertion  of  the  mufcles  or  ideas,  which  are 
moft  frequently  connected  with  volition ; and  they  are  thence 
fubject  to  locked  jaw,  convuliions,  epilepfy,  and  mania,  as  ex- 
plained in  Sect.  XXXIV.  Thofe  of  this  temperament  attend 
to  the  flighted:  irritations  or  fenfations,  and  immediately  exert 
themfelves  to  obtain  or  avoid  the  objects  of  them ; they  can  at 
the  fame  time  bear  cold  and  hunger  better  than  others,  of  which 
Charles  the  Twelfth  of  Sweden  was  an  inftance.  They  are 
fluted,  and  generally  prompted  to  all  great  exertions  of  genius  or 
labour,  as  their  deiires  are  more  extenfive  and  more  vehement, 
and  their  powers  of  attention  and  of  labour  greater.  It  is  this 
facility  of  voluntary  exertion  which  diftinguifhes  men  from 
brutes,  and  which  has  made  them  lords  oi  the  creation. 

IV.  The 


264  OF  TEMPERAMENTS.  Sect.  XXXI.  4,  5 


IV.  The  Temperament  vf  increafed  Affociaticn. 

This  conftitution  confifts  in  the  too  great  facility,  with 
which  the  fibrous  motions  acquire  habits  of  affoci&tion.  anti 
by  which  thefe  afiociations  become  propovtionabiy  ftronger 
than  in  thofe  of  the  other  temperaments.  Thofe  of  this  tem- 
perament are  flow  in  voluntary  exertions,  or  in  thofe  depend- 
ent on  fenfation,  or  on  irritation.  Hence  great  memories.have 
been  Paid  to  be  attended  with  lefs  fenfe  and  lefs  imagination, 
from  Ariftotle  down  to  the  prefent  time ; for  by  the  word  me- 
mory thefe  writers  only  underftood  the  unmeaning  repetition 
of  words  or  numbers  in  the  order  they  were  received,  without 
any  voluntary  efforts  of  the  mind. 

In  dais  temperament  thofe  aflfociatious  of  motions,  which  are 
commonly  termed  Empathies,  a£t  with  greater  certainty  and 
energy,  as  thofe  between  difturbed  vifion  and  the  inverfion  of 
the  motion  ot  the  ftomach,  as  in  fea-ficknefs,  and  the  pains  iu 
the  ihoulder  from  hepatic  inflammation.  Add  to  this,  that  the 
catenated  circles  oi  actions  are  of  greater  extent  than  in  the  other 
coiiftitutions.  Thus,  if  a ftrong  vomit  or  cathartic  be  exhibited 
in  this  temperament,  a fmaller  quantity  will  produce  as  great 
an  effect,  if  it  be  given  fome  weeks  afterwards;  whereas  in  . 
other  temperaments  this  is  only  to  be  expedited,  if  it  be  exhibited 
in  a few  days  after  the  firft  dofe.  Hence  quartan  agues  are 
formed  in  thofe  of  this  temperament,  as  explained  in  Section 
XXXII.  on  difeafes  from  irritation  ; and  other  intermitteuts  are  « 
liable  to  recur  from  flight  caufes  many  weeks  atcer  they  have 
been  cured  by  the  bark. 

V.  The  firft  of  thefe  temperaments  differs  from  the  ftandard 
of  health 'from  defect,  and  the  others  from  excefs  of  fenforial 
power  ; but  it  fometimes  happens  that  the  fame  individual, 
from  the  changes  introduced  into  his  habit  by  the  different  fea- 
l'ons  of  the  year,  modes  or  periods  of  life,  or  by  accidental  dif- 
eafes, paffes  from  one  of  thefe  temperaments  to  another.  Thus 
a long  uie  of  too  much  fermented  liquor  produces  the  tempera- 
ment of  increafed  feniibiiitv ; great  indolence  and  folitude,  that 
of  decreafed  irritability ; and  want  of  the  neceffaries  of  life,  that 
of  increafed  voluntarity. 


SECT. 


Sect.  XXXII.  x.  DISEASES  OF  IRRITATION.  265 

SECT.  XXXII. 

DISEASES  OF  IRRITATION. 

I.  Irritative  fevers  with  firong  pulfe.  With  weak  pulfe. 
Symptoms  of  fever.  Th-'ir  fource.  II.  I.  Quick  pulfe  is- 
owing  to  decreafed  Irritability.  2.  Not  in  feep  or  in  apo- 
plexy. 3.  From  inanition.  Owing  to  deficiency  of  fenforial 
power.  III.  1.  Caujes  of  fever.  From  defeat  of  heat. 
Heat  from  fecretions.  Pain  of  cold  in  the  loins  and  fore- 
head. 2.  Great  expenfe  of  fenforial  power  in  the  vital 
motions-.  Immerji on  infold  water.  Succeeding  glow  of 
heat.  Difficult  refpiration  in  cold  bathing  explained. 
Why  the  cold  bath  invigorates.  Bracing  and  relaxation 
are  mechanical  terms.  3.  Ufes  of  cold  air  in  fevers.  4. 
Ague-fits  from  cold  air.  Whence  their  periodical  returns. 
IV.  Defeat  of  dijiention  a caufe  of  fever.  Deficiency  of 
blood.  Transfufion  of  blood.  V.  1.  Dcfcdt  of  momentum 
of  the  blood  from  mechanic  film  uli.  2.  Air  injefted  into 
the  blood-veffels.  3.  Exercife  increofes  the  momentum  of 
the  blood.  4.  Sometimes  bleeding  incr cafes  the  momentum 
of  it.  VI.  Influence  of  the  fun  and  moon  on  difeajes.  The 
chemical  fiimulus  of  the  blood.  AIenfi.rua.tion  obeys  the 
lunations.  Queries.  VII.  Quie  fence  of  large  glands  a 
caufe  of  fever.  Swelling  of  the  prcecordia.  VIII.  Other 
caufes  of  quiefcence , as  hunger , bad  air , fear , anxiety... 
IX.  1.  Symptoms  of  the  cold  fit.  2.  Gf  the  hot  fit.  3.  Se- 
cond cold  fit  why.  4.  Inflammation  introduced,  or  deli- 
rium, or  fiiipar.  X.  Recapitulation.  Fever  not  an  effort 
of  nature  to  relieve  herjelf.  Doctrine  of  Spafm. 

I.  WHEN  the  contractile  tides  of  the  heart  and  arteries 
perform  a greater  number  of  pulfations  in  a given  time,  and 
move  through  a greater  area  at  each  puliation,  whether  thefe 
motions  are  occaboned  by  the  fiimulus  of  the  acrimony,  or 
quantity  of  the  blood,  or  by  their  affociation  with  other  irrita- 
tive motions,  or  by  the  increafed  irritability  of  the  arterial  fyf- 
tem  ; that  is,  by  an  increafed  quantity  of  tentorial  power,  one 
kind  of  fever  is  produced  ; which  may  be  called  Synocha  irri- 
tativa,  or  Febris  irritativa  pulfu  ford,  or  irritative  fever  with: 
ftrong  pulfe. 

When  the  contractile  Tides  of  the  heart  and  arteries  perform 
a greater  number  of  pulfations  in  a given  time,  but  move 
through  a much  lefs  area  at  each  puliation,  whether  thefe  mo- 
tions are  occafioned  by  defeCt  of  their  natural  feimuli,  or  by  the 


£66  DISEASES  OF  IRRITATION.  Sect.  XXX A.  z. 

defedl  of  other  irritative  motions  with  which  they  are  affoci- 
ated,  or  from  the  inirritability  of  the  arterial  lyftem;  that  is, 
from  a decreafed  quantity  of  fenforial  power,  another  kind  of 
fever  arifes;  which  may  be  termed.  Typhus  irritativus,  or  Fe- 
bris  irritativa  pulfu  debili,  or  irritative  fever  with  weak  pulfe. 
The  former  ot  thefe  fevers  is  the  fynocha  or  nofologifts ; and 
the  latter,  the  typhus  mitior,  or  nervous  fever.  In  the  former, 
there  appears  to  be  an  increafe  of  fenforial  power  ; in  the  lat- 
ter, a deficiency  of  it;  which  is  fhewn  to  be  the  immediate 
caufe  of  ftrength  and  weaknefs,  as  defined  in  Se£t.  XI 1.  1.3. 

It  fhould  be  added,  that  a temporary  quantity  of  ftrength. 
or  debility  may  be  induced  by  the  defedl  or  excels  of  ftimuius 
above  what  is  natural ; and  that  in  the  fame  fever  debility  al- 
ways cxijls  during  the  cold  fit , though  Jlrengih  does  not  al- 
ways exifit  during  the  hot  fit. 

Thefe  fevers  are  always  connected  with,  and  generally  in- 
duced by,  the  difordered  irritative  motions  of  the  organs  of  tenfe, 
or  of  the  inteflinal  canal,  or  ot  tire  glandular  fyflem,  or  of  the 
ablorbent  fyflem;  and  hence  are  always  complicated  with 
fome  or  many  of  thefe  difordered  motions,  which  are  termed 
the  fymptoms  of  the  fever,  and  which  compofe  the  great  variety 
in  thefe  difeafes. 

The  irritative  fevers,  both  with  flrong  and  with  weak  pulfe, 
as  well  as  the  fenfitive  fevers  with  flrong  and  with  weak  pulfe, 
which  are  to  be  deferibed  in  the  next  fedtion,  are  liable  'o  pe- 
riodical remiffions,  and  then  they  take  the  name  of  intermittent 
fevers,  and  are  diflinguilhed  by  the  periodical  times  of  their 
accefs. 

II.  For  the  better  illuftration  of  the  phenomena  of  irritative 
fevers  we  mull  refer  the  reader  to  the  circumftances  of  irrita- 
tion, explained  inSedt.  XII.  and  lhall  commence  tins  -intricate 
fubjecl  by  fpeaking  of  the  quick  pulfe,  ami  proceed  by  conli- 
dering  many  of  the  caules  which  either  leparatelv  or  in  com- 
bination mod  frequently  produce  the  cold  fits  ot  fevers. 

1.  If  the  arteries  are  dilated  but  to  half  their  ufual  diameters, 
though  they  contradl  twice  as  frequently  in  a given  time,  they 
will  circulate  only  half  their  ulual  quantity  ot  blood  ; tor  as 
they  are  cylinders,  the  blood  which  they  contain  mull  be  as 
the  fquares  of  their  diameters.  Hence,  when  the  pulie  becomes 
quicker  and  fmaller  in  the  fame  proportion,  the  heart  and  arte- 
ries adl  with  lefs  eneregy  than  in  their  natural  flate.  See  Sect. 
XII.  1.  4. 

That  this  quick  fmall  pulfe  is  owing  to  want  of  irritability, 
appears,  firft,  becaule  it  attends  other  Ivmptoms  of  want  ot  ir- 
ritability ; and,  fecondly,  becaule,  on  the  application  of  a lli- 

tnulus 


Sect.  XXXII.  2.  DISEASES  OF  IRRITATION.  267 

mulus  greater  than  ufual,  it  becomes  flower  and  larger.  Thus, 
in  cold  fits  of  agues,  in  hyfteric  palpitations  of  the  heart,  and 
when  the  body  is  much  exhaufted  by  haemorrhages,  or  by  fa- 
tigue, as  well  as  in  nervous  fevers,  the  pulfe  becomes  quick 
and  fmall ; and,  fecondlv,  in  all  thofe  cafes,  if  an  iucreafe  of 
ftimulus  be  added,  by  giving  a little  wine  or  opium,  the  quick 
fmall  pulfe  becomes  flower  and  larger,  as  any  one  may  eafily 
fexpericnce  on  himfelf,  by  counting  his  pulfe  after  drinking  one 
or  two  glafies  of  wine,  when  he  is  faint  from  hunger  or  fatigue. 

Now,  nothing  can  fo  ftrongly  evince  that  this  quick  fmall 
pulfe  is  owing  to  defedl  of  irritability,  than  that  an  additional 
ftimulus,  above  what  is  natural,  makes  it  become  flower  and 
larger  immediately : for  what  is  meant  by  a defedd  of  irritabi- 
lity, but  that  the  arteries  and  heart  are  not  excited  into  their 
ufual  exertions  by  their  ufual  quantity  of  ftimulus?  But  if  you 
increafe  the  quantity  of  ftimulus,  and  they  immediately  add 
with  their  ufual  energy,  this  proves  their  previous  want  of  their 
natural  degree  of  irritability.  Thus  the  trembling  hands  of 
drunkards  in  a morning  become  fteady,  and  acquire  ftrength  to 
perform  their  ufual  offices,  by  the  accuftomed  ftimulus  of  a 
glafs  or  two  of  brandy.  . 

2.  In  fleep  and  in  apoplexy  the  pulfe  becomes  flower,  which 
is  not  owing  to  defedf  of  irritability,  for  it  is  at  the  fame 
time  larger  - and  thence  the  quantity  of  the  circulation  is  ra- 
ther increafed  than  diminifhed.  In  thefe  cafes  the  organs  of 
fenfe  are  clofed,  and  the  voluntary  power  is  fufpended  ; while 
the  motions  dependent  on  internal  irritations,  as  thofe  of  digef- 
tion  and  fecretion,  are  carried  on  with  more  than  their  ufual 
vigour ; which  has  led  fuperficial  obfervers  to  confound  thefe 
cafes  with  thofe  arifing  from  want  of  irritability.  Thus  if  you 
lift  up  the  eye-lid  of  an  apopledfic  patient,  who  is  not  actually 
dying,  the  iris  will,  as  ulual,  contradf  itfelf,  as  this  motion  is 
aflociatcd  with  the  ftimulus  of  light ; but  it  is  not  fo  in  the  laft 
ftages  of  nervous  fevers,  where  the  pupil  of  the  eye  continues 
expanded  in  the  broad  day-light : in  the  former  cafe  there  is  a 
want  of  voluntary  power ; in  the  latter,  a want  of  irritability. 

Hence  alfo  thofe  conftitutions  which  are  deficient  in  quantity 
of  irritability,  and  which  pofiefs  too  great  fenfibility,  as  during 
the  pain  of  hunger,  of  hyfteric  fpafrns,  or  nervous  head-achs,  are 
generally  fuppofed  to  have  too  much  irritability ; and  opium, 
which  in  its  due  dofeis  a moft  powerful  ftimulant,  is  erroneoufly 
called  a fedative ; becaufe,  by  increaftng  the  irritative  motions, 
it  decreafes  the  pains  arifing  from  defedt  of  them. 

Why  the  pulfe  flrould  become  quicker  both  from  an  increafe 
•f  irritation,  as  in  the  fynocha  irritativa,  or  irritative  fever  with 

N n ftrong 


263'  DISEASES  OF  IRRITATION-.  Sect.  XXXII.  * 

ftrong  pulfe  ; and  from  the  decreafe  of  it,  as  in  the  typhus  i rri  - 
tativus,  or  irritative  fever  with  weak  pulfe  ; feems  paradoxical. 
The  former  circumftance  needs  no  illuftration  ; fince,  if  die  fti- 
mulus  of  the  blood,  or  the  irritability  of  the  l'anguiferous  iyftem, 
be  increafed,  and  the  ftrength  of  the  patient  not  diminifhed,  it  is- 
plain; that  the  motions  muft  be  performed  quicker  and  ftronger. 

In  the  latter  circumftance,  the  weaknefs  of  the  mufcular 
power  of  the  heart  is  foon  over-balanced  by  die  elafticitv  of 
the  coats  of  the  arteries,  which  they  poflefs  bel'ides  a mufcu- 
lar power  of  contradlion ; and  hence  die  arteries  are  diftend- 
ed  to  lefs  than  their  ufual  diameters.  The  heart  being  tliut 
Hopped  when  it  is  but  half  emptied,  begins  fooner  to  dilate 
again ; and  the  arteries  being  dilated  to  leis  than  their  ufual 
diameters,  begin  fo  much  fooner  to  contradl  themfelves  ; in- 
fomuch,  that  in  the  laft  ftages  of  fevers,  with  weaknefs,  the  fre- 
quency of  puliation  of  the  heart  and  arteries  becomes  doubled  ; 
which,  however,  is  never  the  cafe  in  fevers  widi  ftrength,  in 
which  they  fcldom  exceed  1 1 8 or  120  pulfations  in  a minute. 
It  muft  be  added,  that  in  thefe  cafes,  while  the  pulfe  is  very 
.{mall  and  very  quick,  the  heart  often  feels  large,  and  labour- 
ing to  one’s  hand;  which  coincides  with  die  above  explana- 
tion, {hewing  that  it  does  not  completely  empty  itfelf. 

3.  In  cafes  however  of  debility  from  paucity  of  blood,  as  in 
animals  which  are  bleeding  to  death  in  the  fiaughter-houfe,  the 
quick  pulfations  of  the  heart  and  arteries  may  be  owing  to  their 
not  being  diftended  to  more  than  half  their  ufual  diaftole;  and 
in  confequence  they  muft  contradl  fooner,  or  more  frequently, 
in  a given  time.  As  weak  people  are  liable  to  a deficient  quan- 
tity of  blood,  this  caufe  may  occaftonally  contribute  to  quicken 
the  pulfe  in  fevers  with  debility,  which  may  be  known  bv 
applying  one’s  hand  upon  the  heart  as  above ; but  the  prin- 
cipal caufe  I fuppofe  to  confift  in  the  diminution  of  fenlorial 
power.  When  a mufcle  contains,  or  is  fupplied  with  but  lit- 
tle fenforial  power,  its  contraction  foon  ceaies,  and  in  confe- 
quence may  foon  recur,  as  is  feen  in  the  trembling  hands  of 
people  weakened  by  age  or  by  drunkennefs.  See  Sedt.  XII. 

1.4.  XII.  3.  4. 

It  may,  neverthelefs,  frequently  happen,  that  both  the  defi- 
ciency of  ftimulus,  as  where  the  quantity  of  blood  is  leflened, 
(as  defcribed  in  No.  4.  of  this  ledlion,)  and  the  deficiency  of 
fenforial  power,  as  in  thofe  of  the  temperament  of  inirritabiiitv, 
defcribed  in  Sedt.  XXXI.  occur  at  the  fame  time;  which  will 
thus  add  to  the  quicknefs  of  the  pulfe,  and  to  the  danger  of  the 
dileafe. 

III.  1.  A certain  degree  of  heat  is  neceflary  to  mufcular 

motion. 


Sect. XXXII.  3.  DISEASES  OF  IRRITATION.  269 

•motion,  and  is,  in  confequence,  effential  to  life.  This  is  ob- 
served in  thofe  animals  and  infedts  which  pais  the  cold  feafon 
in  a torpid  fiiate,  and  which  revive  on  being  warmed  by  the 
fire.  This  neceffary  ftimulus  of  heat  has  two  fources  ; one 
from  the  fluid  atmofphere  of  heat,  in  which  all  things  are  im- 
merfed,  and  the  other  from  the  internal  combinations  of  the  par- 
ticles, which  form  the  various  fluids,  which  are  produced  in 
the  extenfivefyftems  of  the  glands.  When  either  the  external 
heat,  which  furrounds  us,  or  the  internal  production  of  it  be- 
comes leffened  to  a certain  degree,  the  pain  of  cold  is  perceived. 

This  pain  of  cold  is  experienced  raofl  fenfibly  by  our  teeth, 
.-when  ice  is  held  in  the  mouth,  or  by  our  whole  fyftem  after 
having  been  pre-vioufly  accuftomed  to  much  warmth.  It  is 
.probable,  that  this  pain  does  not  arife  from  the  mechanical  or 
■chemical  effedts  of  a deficiency  of  heat;  but  that,  like  the  or- 
gans of  fenfe  by  which  we  perceive  hunger  and  thirft,  this  fenfe 
of  heat  fuffers  pain,  when  the  ftimulus  of  its  objedl  is  wanting 
to  excite  the  irritative  motions  of  the  organ;  that -is,  when  the 
fenforial  power  becomes  too  much  accumulated  in  the  quie- 
scent fibres.  See  Sedfion  XII.  5.  3.  For  as  the  periftaltic  mo- 
tions of  the  ftomach  are  leffened,  when  the  pain  of  hunger  is 
.great,  fo  the  adtion  of  the -cutaneous  capillaries  are  leffened  dur- 
ing the  pain  of  cold;  as  appears  by  the  palenefs.of  the  ikin, 
as  explained  in  Sedl.  XIV.  6.  on  the  production  of  ideas. 

The  pain  in  the  fmall  of  the  back  and  forehead  in  the  cold 
-fits  of  the  ague,  in  nervous  hemicrania,  and  in  hyfteric  parox- 
yfms,  when  all  the  irritative  motions  are  much  impaired,  feems 
to  arife  from  this  caufe ; the  vefRls  of  thefe  membranes  or  muf- 
cles  become  torpid  by  their  irritative  affociations  with  other 
parts  of  the  body,  and  thence  produce  lefs  of  their  accuftomed 
fecretions,  and  in  coniequence  lets  heat  is  evolved,  and  they 
experience  the  pain  of  .cold;  which  coldnels  may  often  be  felt 
by  the  hand  applied  upon  the  affedted  part. 

2.  The  importance  of  a greater  or  lefs  deduction  of  heat 
from  the  fyftem  will  be  more  eafy  to  comprehend,  if  we  firft 
confider  the  greajt  expenfe  of  fenforial  power  ufed  in  carrying 
on  the  vital  motions ; that  is,  which  circulates,  abforbs,  fe- 
cretes,  aerates,  and  elaborates  the  whole  mafs  of  fluids  with 
unceafing  afliduicy.  The  fenforial  power,  or  fpirit  of  anima- 
tion, ufed  in  giving  perpetual  and  ftrong  motion  to  the  heart, 
which  overcomes  the  elafticity  and  vis  inertias  of  the  whole  ar- 
terial fyffem;  next  the  expenfe  of  fenforial  power  in  moving 
with  great  force  and  velocity  the  innumerable  trunks  and  rami- 
fications of  the  arterial  fyftem ; the  expenfe  of  fenforial  power 
in  circulating  the  whole  mafc  of  blood  through  the  long  and 
, intricate 


£7o  DISEASES  OF  IRRITATION.  Sect.  XXXII.  3. 

intricate  intentions  of  the  very  fine  veflfels,  which  compofelhe 
glands  and  capillaries;  then  the  expenfe  of  fenlorial  power  in 
the  exertions  of  the  abforbent  extremities  of  all  the  ladteals,  and 
of  all  the  lymphatics,  which  open  their  mouths  on  the  exter- 
nal furface  of  the  fkin,  and  on  the  internal  furfaces  of  every 
cell  or  interftice  of  the  body ; then  the  expenfe  of  fenlorial 
power  in  the  venous  abforption  bv  which  the  blood  is  received 
from  the  capillary  vefTels,  or  glands,  where  the  arterial  power 
ceafes  and  is  drank  up,  and  returned  to  the  heart;  next  th# 
expenfe  of  fenforial  power  ufed  by  the  mufcles  of  refpiration  in 
their  office  of  perpetually  expanding  the  bronchia,  or  air-vef- 
fels,  of  the  lungs ; and  laftly,  in  the  unceahng  periftaltic  r - tions 
of  the  ftomach  and  whole  fyftem  of  inteflines,  and  in  all  the 
fecretions  of  bile,  gaftric  juice,  mucus,  perfpirable  matter,  and 
the  various  excretions  from  the  fyftem.  If  we  conftuei  the 
.ceafelefs  expenfe  of  fenlorial  power  thus  perpetually  employed, 
it  will  appear  to  be  much  greater  in  a day  than  all  the  volun- 
tary exertions  of  our  mufcles  an?  organs  of  fenfeconfume  in  a 
week;  and  all  this  without  any  fenfible  tatigue  ! Now,  if  but 
a part  of  thefe  vital  motions  are  impeded,  or  totally  ft  pped  for 
but  a Ihort  time,  we  gain  an  idea,  that  there  mull  be  a rreat  ac- 
cumulation of  fenforial  power;  as  its  production  in  thefe  or- 
gans, which  are  fubjedb  to  perpetual  activity,  is  continued 
during  their  quiefcence,  and  is  in  confequence  accumulated. 

Whilp,  on  the  contrary,  where  thofe  vital  organs  adt  too 
forcibly  by  increafe  of  ftimulus  without  a proportionally  in- 
creafed  production  of  fenforial  power  in  the  hrain,  it  is  evident, 
that  a great  deficiency  of  adtion,  that  is,  torpor,  muft  foon  fol- 
low, as  in  fevers ; whereas  the  locomotive  muicles,  which  adt 
only  by  intervals,  are  neither  liable  to  fo  great  accumulation  of 
fenforial  power  during  their  times  of  inactivity,  nor  to  fo  great 
an  exhauftion  of  it  during  their  times  of  adtion. 

Thus,  on  going  into  a very  cold  bath,  fuppofe  at  33  degrees 
of  heat  on  Fahrenheit’s  fcale,  the  adtion  of  the  fubcutaneous 
capillaries  or  glands,  and  of  the  mouths  of  the  cutaneous  abfor- 
bents,  is  diminifhed,  or  ceafes  for  a time.  Hence  lefs  or  no 
blood  paflfes  thefe  capillaries,  and  palenefs  fucceeds.  but  foon 
after  emerging  from  the  bath,  a more  florid  colour  3nd  a greater 
degree  of  heat  is  generated  on  the  fkin  than  was  poflefled 
before  iinmerfion ; for  the  capillary  glands,  after  this  quielcent 
ftate,  occafioned  by  the  want  of  ftimulus,  become  more  irrita- 
ble than  ufual  to  their  natural  ftimuli,  owing  to  the  accumula- 
tion of  fenlorial  power,  and  hence  a greater  quantity  of  blood 
is  tranfmitted  through  them,  and  a greater  fecretion  of  perfpira- 
ble matter ; and,  in  confequence,  a greater  degree  of  heat  fuc- 
ceeds. 


Sect.  XXXII.  3.  DISEASES  OF  IRRITATION.  271 

ceeds.  During  the  continuance  in  cold  water  the  breath  is  cold, 
and  the  adlof  refpiration  quick  and  laborious  ; which  have  ge- 
nerally been  afcribed  to  the  obftruction  of  the  circulating  fluid 
by  a fpafm  of  the  cutaneous  veflels,  and  by  a confcquent  accu- 
mulation of  blood  in  the  lungs;  occafioned  by  the  preflure  as 
well  as  by  the  coldnefs  of  the  water.  This  is  not  a fatisfaclory 
account  of  this  curious  phenomenon,  flnce,  at  this  time,  the 
whole  circulation  is  lefs,  as  appears  from  the  fmallnefs  of  the 
pulfe,  and  coldnefs  of  the  breath ; which  fhew  that  lefs  blood  paf- 
fes  through  the  lungs  in  a given  time.  The  fame  laborious  breath- 
ing immediately  occurs  when  the  palenefs  of  the  fkin  is  produced 
by  fear,  where  no  external  cold  or  preflure  is  applied. 

The  minute  veflels  of  the  bronchia,  through  which  the  blood 
pafles  from  the  arterial  to  the  venal  fyftem,  and  which  corref- 
pond  with  the  cutaneous  capillaries,  have  frequently  been  expof- 
ed  to  cold  air,  and  become  quiefcent  along  with  thofe  of  the 
fkin ; and  hence  their  motions  are  fo  aflbciated  together,  that 
when  one  is  affedled  either  with  quiefcence  or  exertion,  the 
other  fympathizes  with  it,  according  to  the  laws  of  irritative 
aflociation.  See  Sedt.  XXVII.  1.  on  Haemorrhages. 

Belides  the  quiefcence  of  the  minute  veflels  of  the  lungs, 
there  are  many  other  fyftems  of  veflels  which  become  torpid 
from  their  irritative  afloeiations  with  thofe  of  the  fkin,  as  the 
abforbents  of  the  bladder  and  inteflines ; whence  an  evacuation  of 
pale  urine  occurs,  when  the  naked  fkin  is  expoled  only  to  the 
coldnefs  of  the  atmofphere;  and  fprinkling  the  naked  body  with 
cold  water  is  known  to  remove  even  pertinacious  conftipation 
of  the  bowels.  From  the  quiefcence  of  fuch  extenfive  fyftems  of 
veflels  as  the  glands  and  capillaries  of  the  fkin,  and  the  minute 
veflels  of  the  lungs,  with  their  various  abforbent  feries  of  veflels, 
a great  accumulation  of  fenforial  powers  is  occafioned;  part  of 
which  is  again  expended  in  the  increafed  exertion  of  all  thefe 
veflels,  with  an  univerfal  glow  of  heat  in  confequence  of  this 
exertion,  and  the  remainder  of  it  adds  vigour  to  both  the  vital 
and  voluntary  exertions  of  the  whole  day. 

If  the  adlivity  of  the  fubcutaneous  veflels,  and  of  thofe  with 
which  their  aclions  are  aflbciated,  was  too  great  before  cold 
-immerlion,  as  in  the  hot  days  of  fummer,  and  by  that  means 
the  fenforial  power  was  previoufly  diminifhed,  we  fee  the  caul'e 
why  the  cold  bath  .gives  fuch  prefent  ftrength ; namely,  by  flop- 
ping the  unneceflary  activity  of  the  fubcutaneous  veflels,  and 
thus  preventing  the  too  great  exhauftion  of  fenforial  power; 
which,  in  metaphorical  language,  has  been  called  bracing  the 
■fyftem ; which  is,  however,  a mechanical  term,  only  applica- 
ble to  drums,  or  muflcal  firings ; as,  on  the  contrary,  the  word 

relaxation , 


272  DISEASES  OF  IRRITATION.  Sect.  XXXII.  3. 

relaxation , when  applied  to  living  animal  bodies,  can  only 
mean'too  fmall  a quantity  of  ftimulus,  or  too  fmall  a quantity 
of  fenforial  power;  as  explained  in  Se£t.  XII.  1. 

3.  This  experiment  ol  cold  bathing  prefents  us  with  a funple 
fever-fit;  fo,r  the  pulfe  is  weak,  fmall  and  quick  during  the 
cold  immerfion,  and  becomes  ftrong,  full  and  quick  during  the 
fubfequent  glow  of  heat ; till,  in  a few  minutes,  thefe  fymptoms 
fubfide,  and  the  temporary  fever  ceafes. 

In  thofe  conftitutions  where  the  degree  of  inirritabilitv,  or  of 
debility,  is  greater  than  natural,  the  coldnefs  and  palenels  of  the 
fkin,  with  quick  and  weak  pulfe,  continue  a long  time  after  the 
patient  leaves  the  bath ; and  the  fubfequent  heat  approaches  by 
unequal  flufhings,  and  he  feels  himfelt  difordered  for  mauy 
hours.  Hence  the  bathing  in  a cold  fpring  of  water,  where  the 
heat  is  but  forty-eight  degrees  on  Fahrenheit’s  thermometer, 
much  difagrees  with  thofe  of  weak  or  inirritable  habits  of  body, 
who  poiTefs  fo  little  denforial  power,  that  they  cannot,  without 
injury,  bearto  have itdiminifhed  even  fora  fhort  time  ; but  who 
can  neverthelefs  bear  the  more  temperate  coldnefs  of  Buxton 
bath,  which  is  about  eighty  degrees  of  heat,  and  which  ftrength- 
ens  them,  and  makes  them  by  habit  lefs  liable  to  great  quie- 
scence from  fmall  variations  of  cold,  and  thence  lefs  liable  to  be 
difordered  by  the  unavoidable  accidents  of  life.  Hence  it  ap- 
pears, why  people  of  thefe  inirritable  conftitutions,  which  is  an- 
other expreilion  for  fenforial  deficiency,  are  often  much  injured 
by  bathing  in  a cold  fpring  of  water ; and  whv  they  fhould 
continue  but  a very  fhort  time  in  baths,  which  are  colder  than 
their  bodies;  anJ  fhould  gradually  increafe  both  the  degree  of 
coldnefs  of  the  water,  and  the  time  of  their  continuance  in  it, 
if  they  would  obtain  faiutary  effects  from  cold  immerfions. — 
See  Se6I.  XII.  2.  1. 

On  the  other  hand,  in  all  cafes  where  the  heat  of  the  external 
furface  of  the  body,  or  of  the  internal  furface  of  the  lungs,  is 
greater  than  natural,  the  ufe  of  expolureto  cool  air  may  be  de- 
duced. In  fever-fits,  attended  with  ftrength,  that  is,  with  great 
quantity  of  fenforial  power,  it  removes  the  additional  ftimulus 
of  heat  from  the  furfaces  above  mentioned,  and  thus  prevents 
their  excefs  of  ufelefs  motion;  and  in  fever-fits,  attended  with 
debility,  that  is,  with  a deficiency  of  the  quantity  of  fenforial 
power,  it  percents  the  great  and  dangerous  wafte  of  fenforial 
power  expended  in  the  unneceflary  increafe  ot  the  actions  ot 
the  glands  and  capillaries  of  the  fkin  and  lungs. 

4.  In  the  fame  manner,  when  any  one  is  long  expofed  to 
very  cold  air.  a quielcence  is  produced  ot  the  cutaneous  and 
pulmonary  capillaries  and  abforbents,  owing  to  the  deficiency 

of 


Sect.  XXXII.  4.  DISEASES  OF  IRRITATION.  273. 

of  their  ufual  ftimulus  of  heat : and  this  quiefcence  of  fo  great 
a quantity  of  vefiels  affefts,  by  irritative  aflociation,  the  whole 
abforbent  and  glandular  fyftem,  which  becomes  in  a greater  or 
lefs  degree  quiefcent,  and  a cold  fit  of  fever  is  produced. 

If  the  deficiency  of  the  ftimulus  or  heat  is  very  great,  the 
quiefcence  becomes  fo  general  as  to  extinguifh  life,  as  in  thofe 
who  are  frozen  to  death. 

If  the  deficiency  of  heat  be  in  lefs  degree,  but  yet  fo  great  as 
in  fome  meal'ure  to  diforder  the  fyftem,  and  fhould  occur  the 
fucceeding  day,  it  will  induce  a greater  degree  of  quiefcence 
than  before,  from  its  acting  in  concurrence  with  the  period  of 
the  diurnal  circle  of  afitions,  explained  in  Se£t.  XXXVI. — 
Hence,  from  a fmall  beginning  a greater  and  greater  degree  of 
quiefcence  may  be  induced,  till  a complete  fever-fit  is  formed  ; 
and  which  will  continue  to  recur  at  the  periods  by  which  it 
was  produced.  See  Se£t.  XVII.  3.  6. 

If  the  degree  of  quiefcence  occafioned  bydefedt  of  the  ftimulus 
of  heat  be  very  great,  it  will  recur  a fecond  time  by  a flighter 
caufe  than  that  which  firft  induced  it.  If  the  caufe  which  in- 
duces the  fecond  fit  of  quiefcence  recurs  the  fucceeding  day,  the 
quotidian  fever  is  produced ; if  not  till  the  alternate  day,  the  ter- 
tian fever;  and  if  not  till  after  feventy-two  hours  from  the  firft 
fit  of  quiefcence,  the  quartan  fever  is  formed.  This  laft  kind 
of  fever  recurs  lefs  frequently  than  the  other,  as  it  is  a difeafe 
only  of  thofe  of  the  temperament  of  affociability,  as  mentioned 
in  Seel.  XXXI.  for  in  other  conflitutions  the  capability  of 
forming  a habit  ceafes,  before  the  new  caufe  of  quiefcence  is 
again  applied,  if  that  does  not  occur  fooner  than  in  feventy- 
two  hours. 

And  hence  thofe  fevers,  whofe  caufe  is  from  cold  air  of  the 
night  or  morning,  are  more  liable  to  obferve  the  l'olai  day  in 
their  periods ; while  thofe  from  other  caufes  frequently  obferve 
the  lunar  day  in  their  periods,  their  paroxyfms  returning  near 
an  hour  later  every  day,  as  explained  in  Se£t.  XXXVI. 

IV.  Another  frequent  caufe  of  the  cold  fits  of  fever  is  the 
defe£t  of  the  ftimulus  of  diftention.  The  whole  arterial  fyf- 
tem would  appear,  by  the  experiments  of  Haller,  to  be  irrita- 
ble by  no  other  ftimulus ; and  the  motions  of  the  heart  and  ali- 
mentry  canal  are  certainly  in  fome  meal'ure  dependent  on  the 
lame  caufe.  See  Se£t.  XIV.  7.  Hence  there  can  be  no  won- 
der, that  the  diminution  of  diftention  fhould  frequently  induce 
the  quielcence,  which  conftitutes  the  beginning  of  fever-fits. 

Monfieur  Lieutaud  has  judicioufly  mentioned  the  deficiency 
of  the  quantity  of  blood  amongft  the  caufes  of  difeafes,  which 
he  fays  is  frequently  evident  in  difiedlions : fevers  are  hence 

brought 


274  DISEASES  OF  IRRITATION.  Sect.  XXXII.  5 

brought  on  by  great  haemorrhages,  diarrhoeas,  or  other  evacua- 
tions; or  from  the  continued  ufe  of  diet,  which  contains  but 
little  nourifhment ; or  from  rhe  exhauftion  occafioned  by  vio- 
lent fatigue,  or  by  thofe  chronic  diieai'es  in  which  the  digeftion 
is  much  impaired  ; as  where  the  ftomach  has  been  long  effect- 
ed with  the  gout  or  fchirrus;  or  in  die  paralylis  of  the  liver,  as 
defcribed  in  Se£t.  XXX.  Hence  a paroxyfm  of  gout  is  liable 
to  recur  on  bleeding  or  purging  ; as  the  torpor  of  fome  vifcus, 
which  precedes  the  inflammation  of  die  foot,  is  thus  induced  by 
the  want  of  the  flimulus  of  diftention.  And  hence  the  extre- 
mities of  the  body,  as  the  nofe  and  fingers,  are  more  liable  to 
become  cold,  when  we  have  long  abftained  from  food ; and 
hence  the  pulfe  is  increaved,  both  in  ftrength  and  velocity,  above 
the  natural  ftandard,  after  a full  meal,  by  the  ftimulus  of  diften- 
tion. 

However,  this  ftimulus  of  diftention,  like  the  ftimulus  of 
heat  above  defcribed,  though  it  contributes  much  to  die  doe  ac- 
tion not  only  of  the  heart,  arteries,  and  alimentary  canal,  but 
fecms  neceftary  to  the  proper  fecreuon  of  all  the  various  glands  ; 
yet,  perhaps  it  is  not  the  foie  caufe  of  any  of  thefe  numerous 
motions ; for  as  the  ladfeals,  cutaneous  abforbents,  and  the  va- 
rious glands  appear  to  be  ftimulated  into  action  by  the  peculiar 
pungency  of  the  fluids  they  abforb ; fo  in  the  inteftinal  canal 
the  pungency  of  the  digefting  aliment,  or  the  acrimonv  of  the 
feces,  feem  to  contribute,  as  well  as  their  bulk,  to  promote  the 
periftaltic  motions;  and  in  the  arterial  fyftem,  the  momentum 
of  the  particles  of  the  circulating  blood,  and  their  acrimonv,  fti- 
mulate  the  arteries,  as  well  as  the  diftention  occafioned  by  in 
Where  the  pulfe  is  fmall,  this  defedh  of  diftention  is  piefent,  and 
contributes  much  to  produce  the  febris  irritativa  pullu  debili, 
or  irritative  fever  with  weak  pulfe,  called  by  modern  writers 
nervous  fever,  as  a predifponent  caufe.  See  Setft.  XII.  1.  4. 
Might  not  the  transfuflon  of  blood,  fuppofe  of  four  ounces  daily 
from  a ftrong  man,  or  other  healthful  animal,  as  a fheep  cr 
an  afs,  be  ufed  in  the  earlv  ftate  of  nervous  or  putrid  fevers  with 
great  profpeift  of  iuccefs? 

V.  The  ilefecl  of  the  momentum  of  the  panicles  of  the  circu- 
lating blood  is  another  caufe  of  the  quiefceuce,  with  which  the 
cold  fits  of  fever  commence.  This  ftimulus  of  the  momentum 
of  the  progreffive  particles  of  the  blood  does  not  act  over  the 
whole  body  like  thofe  of  heat  and  diftention  above  defcribed, 
but  is  confined  to  the  arteral  fyftem,  and  differs  from  the  ftimu- 
Il  s of  the  diftention  ok  the  blood  as  much  as  the  vibration  of 
the  air  docs  from  the  currents  of  it.  Thus  are  the  different 
organs  of  our  bodies  ftimulated  by  four  different  mechanic  pro- 
perties, 


Sect.  XXXII. 5<  DISEASES  OF  IRRITATION.  275 

perries  of  the  external  world  : the  fenfe  of  touch  by  the  pref- 
fure  of  folid  bodies,  fo  as  to  diftinguifh  their  figure ; the  mufeu- 
lar  fyftem  by  the  diftention  which  they  occafion ; the  inter- 
nal fin-face  of  the  arteries,  by  the  momentum  of  their  moving 
particles;  and  the  auditory  nerves,  by  the  vibration  of  them: 
and  thefe  four  mechanic  properties  are  as  different  from  each 
other  as  the  ■ various  chemical  ones,  which  are  adapted  to  the 
numerous  glands,  and  to  the  other  organs  of  fenfe. 

2.  The  momentum  of  the  progeftive  particles  of  blood  is 
compounded  of  their  velocity  and  their  quantity  of  matter  : 
hence,  whatever  circumfiances  dimimfh  either  of  thefe  without 
proportionally  increafing  the  other,  and  without  luperadding 
either  of  the  general  ftimuli  of  heat  or  diftention,  will  tend  to 
produce  a quiefeence  of  the  arterial  fyftem,  and  from  thence  of 
ail  the  other  irritative  motions  which  are  connedled  with  it. 

Hence,  in  all  thofe  conftitutions  or  difeafes  where  the  blood 
contains  a greater  proportion  of  ferurri,  which  is  the  lighteft 
part  of  its  compofttion,  the  pulfation's  of  the  arteries  are  weaker, 
as  in  nervous  fevers,  chlorofts,  and  hyfteric  complaints ; for 
in  thefe  cafes  the  momentum  of  the  progreflive  particles  of 
blood  is  lefs:  and  hence,  where  the  denfer  parts  of  its  compo- 
fition  abound,  as  the  red  part  of  it,  or  the  coagulable  lymph, 
the  arterial  pulfations  are  ftronger ; as  in  thofe  of  robuft  health, 
and  in  inflammatory  difeafes. 

That  this  ftimulus  of  the  momentum  .of  the  particles  of  the 
circulating  fluid  is  of  the  greateft  confequence  to  the  arterial 
adfion,  appears  from  the  experiment  of  injedling  air  into  the 
blood  veffels,  which  feems  to  deftfoy  animal  life  from  the  want 
of  this  ftimulus  of  momentum ; for  the  diftention  of  the  ar- 
teries is  not  dimini  flied  by  it ; it  poftefles  no  corroftve  acrimony, 
and  is  lefs  liable  to  repafs  the  valves  than  the  blood  itfelf;  fiuce 
air-valves  in  all  machinary  require  much  lefs  accuracy  of  con- 
ftrudtion  than  thofe  which  are  oppofed  to  water. 

3.  One  method  of  increafing  the  velocity  of  the  blood,  and 
in  confequence  the  momentum  of  its  particles,  is  by  the  exer- 
cife  of  the  body,  or  by  the  ftidlion  of  its  furface : fo,  on  the 
contrary,  too  great  indolence  contributes  to  decreafe  this,  ftr- 
rftulus  of  the  momentum  of  the  particles  of  the  circulating  blood, 
and  thus  tends  to  induce  quiefeence  ; as  is  feen  in  hyfteric  ca- 
fes, and  chlorofts,  and  the  other  difeafes  of  fedentary  people. 

4.  The  velocity  of  the  particles  of  the  blood  in  certain  cir- 
cuinftances,  is  increafed  by  veneieeftion,  which,  by  removing  a 
part  of  it,  diminifhes  the  reftftance  to  the  motion  of.  the  other 
part,  and  hence  the  momentum  of  the  particles  of  it  is  in- 
creafed. This  may  be  eaiily  underftood  by  conftdering  it  in 

O q the 


ay6  DISEASES  OF  IRRITATION.  Sect.  XXXtt  cV 

the  extreme,  fince,  if  the  refinance  was  greatly  increafed,  fo.- 
as  to  overcome  the  propelling  power,  there  could  be  no  velo- 
city, and  in  confequence  no  momentum  at  all.  From  this  cir- 
eumftance  arifes  that  curious  phenomenon,  the  truth  of  which 
I have  been  more  than  once  witnefs  to,  that  venefedtion  will 
often  inftantaneoufly  relieve  thofe  nervous  pains,  w-hich  attend 
the  cold  periods  of  hvfteric  afthmatic,  or  epileptic  difeafes ; and 
that  even  where  large  dofes  of  opium  have  been  in  vain  ex- 
hibited. In  thefe  cafes,  the  pulie  becomes  ftronger  after  the-- 
bleeding,  and  the  extremities  regain  their  natural  warmth,  and 
an  opiate  then  given,  adds  with  much  more  certain  effedt. 

VI.  There  is  another  caufe,  which  l'eems  occafionally  to 
induce  quiefcence  into  fome  part  of  our  fyftem  ; I mean  the 
influence  of  the  fun  and  moon  : the  attraction  of  thefe  lumi- 
naries, by  decreafing  the  gravity  of  the  particles  of  the  blood,. 
Cannot  affedt  their  momentum,  as  their  vis  inertias  remains 
the  fame ; but  it  may,  neverthelefs,  produce  lome  chemical 
change  in  them,  becaufe  whatever  affects  the  general  attrac- 
tions of  the  particles  of  matter,  may  be  l'uppofed  from  analogy 
to  affedt  their  fpeciflc  attradtions  or  affinities:  and  thus  the 
ftimulus  of  the  particles  of  blood  may  be  dimini  fired,  though 
not  their  momentum.  As  the  tides  of  the  fea  obey  the  fouth- 
ing  and  northing  of  the  moon,  (allowing  for  the  time  neceflary  . 
for  their  motion,  and  the  obflrudfions  of  the  fhores,)  it  is  pro-„ 
bable,  that  there  are  alfo  atmofpheric  tides  on  both  fides  of  the 
earth,  which,  to  the  inhabitants  of  another  planet,  might  fo  de- 
fied! the  light  as  to  refemble  the  ring  of  Saturn.  Now,  as 
thefe  tides  of  water,  or  of  air,  are  railed  by  the  diminution  of 
their  gravity,  it  follows,  that  their  preflure  on  the  furface  of 
the  earth  is  no  greater  than  the  preflure  of  the  other  parts  of 
the  ocean,  or  of  the  atmofphere,  where  no  luch  tides  exift 
and  therefore,  that  they  cannot  a fleet  die  mercury  in  the  ba- 
rometer. In  the  fame  manner  the  gravity  of  all  other  terref- 
trial  bodies  is  diminiflied  at  the  times  of  the  fouthing  and 
northing  of  the  moon,  and  that  in  a greater  degree  when  this- 
coincides  with  the  fouthing  and  northing  of  the  fun,  and  this  in 
a ftill  greater  degree  about  the  times  of  the  equinoxes.  This 
decreal'e  of  the  gravity  of  all  bodies  during  the  rime  the  moon 
paries  our  zenith  or  nadir,  might  poffibly  be  fliewn  by  the  flower 
vibrations  of  a pendulum,  compaied  with  a fpring  clock,  or 
with  aftronomical  obfervation : fince  a pendulum  of  a certain 
.length  moves  flower  at  the  line  than  near  the  poles,  becaule  the 
gravity  being  diminiflied,  and  the  vis  inertia  continuing  the  fame, 
the  motive  power  is  lefs,  but  the  refiflance  to  be  overcome  con- 
tinues the  fame.  Tiie  combined  powers  of  the  lunar  and  i'olar 

attraction 


Sect.  XXXII.  6.  DISEASES  OF  IRRITATION.  277 

.attraction  is  eftimated, by  Sir Ifaac  Newton,  not  to  exceed  one 
7,868,850th  part  of  the  power  of  gravitation,  which  feems  in- 
: deed  but  a fmall  circumftance  to  produce  any  conliderable  ef- 
fe£t  on  the  weight:  of  Sublunary  bodies,  and  yet  this  is  Sufficient 
to  raife  the  tides  at  the  equator  above  ten  feet  high;  and  if  i.t 
be  confidered,  what  fmall  impulfes  of  other  bodies  produce  their 
effects  on  the  organs  of  fenfe  adapted  to  the  perception  of  them, 
as  of  vibration  on  the  auditory  nerves,  we  ftiall  ceafe  to  be  fur- 
prifed,  that  fo  minute  a diminution  in  the  gravity  of  the  parti- 
cles of  blood  fhould  fo  far  affect  their  chemical  changes,  or 
their  Stimulating  quality,  as,  joined  with  other  caufes,  Some- 
times to  produce  the  beginnings  of  difeafes. 

Add  to  this,  that  if  the  lunar  influence  produces  a very  Small 
.degree  of  quiefcence  at  flrft,  and  if  that  recurs  at  certain  pe- 
riods, even  with  lefs  power  to  produce  quiefcence  than  at  firft, 
yet  the  quiefcence  will  daily  increafe  by  the  acquired  habit  act- 
ing, at  the  fame  time,  till,  at  length,  fo  great  a degree  of  quie- 
fcence is  induced  as  to. produce  phrenfy,  canine  madnefs,  epi- 
lepfy,  hyfteric  pains,  or  cold  -fits  of  fever ; inftances  of  many 
,of  which  are  to  be  found  in  Dr.  Mead’s  work  on  this  fubjecSL 
The  folar  influence  alfo  appears  daily  in  Several  difeafes  ; but 
as  darknels,  Silence,  fleep,  and  our  periodical  meals,  mark  the 
parts  of  the  folar  circle  of  fcdlidfts,  it  is' Sometimes  dubious  to 
which  of  thefe  the  periodical  returns  of  thele  difeafes  are  to  be 
aferibed.  ■ 

As  far  as  I have  been  able  to  obferve,  the  periods  of  inflam- 
matory difeafes  obferve  the  folar  day;  as  the  gout  and  rheuma- 
tifm  have  their  greateft  quiefcence  about  noon  and  midnight, 
and  their  exacerbations  fome  hours  after;  as  they  have  more 
frequently  their  immediate  caufe  from  cold  air,  inanition,  or 
fatigue,  than  from  the  effects  of  lunations ; whilft  the  cold  fits 
of  hyfteric  patients,  and  thofe  in  nervous  fevers,  more  fre- 
quently occur  twice  a day,  later  by  near  half  an  hour  each  time* 
according  to  the  lunar  day  ; whilft  feme  fits  of  intermittents, 
which  are  undifturbed  by  medicines,  return  at  regular  folar  pe- 
riods, and  others  at  lunar  ones;  which  may  probably  be  owing 
to  the  difference  of  the  periods  of  thofe  external  eircumftances  of 
cold,  inanition,  or  lunation,  which  immediately  caufed  them. 

We  muft,  however,  obferve,  that  the  periods  of  quiefcence 
and  exacerbation  in  difeafes  do  not  always  commence  at  the 
times  of  the  fyzygies  or  quadratures  of  the  moon  and  fun,  or  at 
the  times  of  their  paffxng  the  zenith  or  nadir;  but  as  it  is  proba- 
ble, that  the  ftimulus  ol  the  particles  of  the  circumfluent  blood 
is  gradually  diminiflred  from  the  time  of  the  quadratures  to,  that  of 
the  fyzigyes,  the  quiefence  may  commence  at  any  hour,  when, 

co-operating 


278  DISEASES  OF  IRRITATION.  Sect. XXXII.  6. 


co-operating  with  other  caufes  of  qu.efcence,  it  becomes  great  j 
enough  to  produce  a difeafe : afterwards  it  will  continue  to  recur 
at  the  fame  period  of  the  lunar  orfolar  influence ; the  famecaule 
operating  conjointly  with  the  acquired  habit,  that  is,  with  die 
catenation  of  this  new  motion  with  the  diffevered  links  of  the 
lunar  or  folar  circles  of  animal  adtion. 

In  this  manner,  the  periods 'of  menftruation  obey  the  lunar 
month  with  great  exadtnefs  in  healthy  patients,  (and  perhaps 
the  venereal  orgafin  in  brute  animals  does  the  fame)  yet  theft 
periods  do  not  commence,  either  at  the  fyzygies  or  quadra- 
tures of  the  lunations;  but  at  whatever  time  of  the  lun.ir  pe- 
riods they  begin,  they  obferve  the  fame  in  their  returns  till 
dome  greater  caufe  disturbs  them. 

Hence,  though  the  heft  way  to  calculate  the  time  of  the  ex- 
pected returns  of  the  paroxyfms  of  periodical  difeafes  is  to 
count  the  number  of  hours  between  the  commencement  of  the 
two  preceding  tits,  yet  the  following  observations  may  be  worth 
attending  to,  when  we  endeavour  to  prevent  the  returns  of  ma- 
niacal or  epileptic  difeafes  ; whofe  periods  (at  he  beginning  of 
them  efpeciallv)  frequently  obferve  the  fyzygies  of  the  moon 
and  fun,  and  particularly  about  the  equinox. 

The  greatefc  of  the  two  tides  happening  in  every  revolution 
of  the  moon,  is  that  when  the  mqpri  approaches  neareft  to  the 
zenith  or  nadir ; for  this  reafon,  virile  the  fun  is  in  die  northern 
figns,  that  is, during  the  vernal  and  fummer  months,  the  greater  J 
of  the  two  diurnal  titles  in  our  latitude  is  that  when  the  moon 
is  above  the  horizon;  and  when  the  fun  is  in  the  foudiern 
figns,  or  during  the  autumnal  and  winter  months,  the  greater 


tide  is  that  which  arifes  when  the  moon  is  below  the  horizon  : 


and  as  the  fun  approaches  lomewbat  nearer  the  earth  in  win- 
ter than  in  fummer,  the  greateft  equinoxial  tides  are  obferved 
to  be  a little  before  the  venial  equinox,  and  a little  after  the 
autumnal  one. 

Do  not  the  cold  periods  of  lunar  difeafes  commence  a few 
hours  before  the  fondling  of  the  moon  during  the  venial  and 
fummer  months,  and  before  the  northing  of  the  moon  during 
the  autumnal  and  winter  months  r Do  not  palfies  and  apoplex- 
ies, which  occur  about  the  equinoxes,  happen  a few  davs  be- 
fore the  vernal  equinoctial  lunation,  and  after  the  autumnal 
one  ? Are  not  the  periods  of  thole  diurnal  difeafes  more  oblii- 
nate,  that  commence  many  hours  before  the  fouthing  or  north- 
ing of  the  moon,  than  of  tliofe  which  commence  at  thofe  time.-  ? 
Are  not  thofe  Dallies  and  apoplexies  more  dangerous  which 
commence  many  days  before  the  fvzygies  of  thp  moon,  than 
thofe  which  happen  at  thofe  times  r See  Seel.  XXXVI.  on 
the  Periods  .of  Difeafes. 


YU.  Another 


Sect.  XXXII.  7, 8.  DISEASES  OF  IRRITATION.  279 

VII.  Another  very  frequent  caufe  of  the  cold  fit  of  fever  is 
the  quiefcence  of  fome  of  thofe  large  congeries  of  glands,  which 
icompofe  the  liver,  fpleen,  or  pancreas;  one  or  more  of  which 
are  frequently  i'o  enlarged  in  the  autumnal  intermittents  as  to  be 
perceptible  to  the  touch  externally,  and  are  called  by  the  vulgar 
ague-cakes.  As  thefe  glands  are  fiimulated  into  aCtion  by  the 
fpeeific  pungency  of  the  fluids  which  they  abforb,  the  general 
caufe  of  their  quiefcence  feems  to  be  the  too  great  infipidity  of 
the  fluids  of  the  body,  co-operating  perhaps  at  the  fame  time 
with  other  general  caufes  of  quiefcence. 

Hence,  in  marfhy  countries  at  cold  feafons,  which  have  fuc- 
ceeded  hot  ones,  and  among!!  thofe  who  have  lived  on  innu- 
tritions and  unftimulating  diet,  thefe  agues  are  moft  frequent. 
The  enlargement  of  thefe  quiefcent  vifcera,  and  thefwelling  of 
the  praseordia  in  many  other  fevers,  is  moft  probably  owing  to 
the  fame  caufe;  which  may  confift  in  a general  deficiency  of 
the  production  of  fenforial  power,  as  v/ell  as  the  diminiflied  fti- 
jnulation  of  the  fluids ; and  when  the  quiefcence  of  fo  great  a 
number  of  glands  as  conftitute  one  of  thofe  large  vifcera  com- 
mences, all  the  other  irritative  motions  are  afFefiled  by  their  con- 
nection with  it,  and  the  cold  fit  of  fever  is  produced. 

VIII.  There  are  many  other  caufes  which  produce  quie- 
fcence of  fome  part  of  thq  animal  fyftem,  as  fatigue,  hunger, 
thirft,  bad  diet,  difappointed  love,  unwholefome  air,  exhauf- 
tion  from  evacuations,  and  many  others ; but  the  laft  caufe 
that  we  fliall  mention,  as  frequently  productive  of  cold  fits  of 
fever,  is  fear  or  anxiety  of  mind.  The  pains  which  we  are  firft 
and  moft  generally  acquainted  with,  have  been  produced  by 
defeCt  of  fome  ftimulus  : thus,  loon  after  our  nativity  we  be- 
come acquainted  with  the  pain  from  the  coldnefs  of  the  air, 
from  the  want  of  refpiration,  and  from  the  want  of  food.  Now, 
all  thefe  pains  occaftoned  by  defeCt  of  ftimulus  are  attended 
with  quiefcence  of  the  organ,  and  at  the  fame  time  wfith  a 
greater  or  Iefs  degree  of  quiefcence  of  other  parts  of  the  fyftem  : 
thus,  if  we  even  endure  the  pain  of  hunger  fo  as  to  mils  one 
meal  inftead  of  our  daily  habit  of  repletion,  not  only  the  pe- 
riftaltic  motions  of  the  ftomach  and  bowels  are  diminifhed,  but 
we  are  more  liable  to  coldnefs  of  our  extremities,  as  of  our  no- 
fes,  and  ears,  and  feet,  than  at  other  times. 

Now,  as  fear  is  originally  excited  by  our  having  experienced 
pain,  and  is  itfelf  a painful  affedion,  the  fame  quiefcence  of 
other  fibrous  motions  accompany  it,  as  have  been  moft  frequent- 
ly conneCted  with  this  kind  of  pain,  as  explained  in  SeCI.  XVI. 
$.  1.  as  the  eokinefs  and  palenefs  of  the  fkin,  trembling,  diffi- 
cult refpiration,  indigeftion,  and  other  fymptoms  which  contri- 
bute 


280  DISEASES  OF  IRRITATION.  Sect.  XXXII.  9. 

bute  to  form  the  cold  fit  of  fevers.  Anxiety  is  fear  continued 
through  a longer  time,  and,  by  producing  chronical  torpor  of 
the  fyftem,  extinguifhes  life  flowly,  by  what  is  commonly 
termed  a broken  heart. 

IX.  i.  We  now  ftep  forwards  to  confider  the  other  fvmp- 
toms  in  confequence  of  the  quiefcence  which  begins  the  fits  of 
fever.  If,  by  any  of  the  circmuftances  before  defcribed,  or  by 
two  or  more  of  them  acting  at  the  fame  time,  a great  degree  of 
quiefcence  is  induced  on  any  confiderable  part  of  the  circle  of 
irritative  motions,  the  whole  clafs  of  them  is  more  or  lei's  dif- 
turbed  by  their  irritative  affociations.  If  this  torpor  be  occa- 
iioned  by  a deficient  fupply  of  feniorial  power,  and  happens  to 
any  of  thcfe  parts  of  the  lyftem  which  are  accuftomed  to  per- 
petual activity,  as  the  vital  motions,  the  torpor  increafes  rapid- 
ly, becaufe  of  the  great  expenditure  of  fenforial  power  by  the 
inceflant  activity  ot  thofe  parts  of  the  fyftem,  as  fhewn  in  No. 

3.  2.  of  this  fedtioir.  Hence  a deficiency  of  all  the  fecretions 
fucceeds;  and  as  animal  heat  is  produced  in  proportion  to  the 
quantity  of  thofe  fecretions,  the  coldnefs  of  the  fkin  is  the  firft 
circumftance  which  is  attended  to.  Dr.  Martin  afleits,  that 
fome  parts  of  his  body  were  warmer  than  natural  in  thecold  ft 
of  fever  ; but  it  is  certain,  that  thofe  which  are  uncovered,  as  I 
the  fingers,  and  nofe,  and  ears,  are  much  colder  to  the  touch, 
and  paler  in  appearance.  It  is  poffible,  that  his  experiments  g 
were  made  at  the  beginning  of  the  fubfequent  hot  fits;  which  2 
commence  with  partial*!  diftributions  of  heat,  owing  to  fome  y 
parts  of  the  body  regaining  their  natural  irritability  fooner  than 
others. 

From  the  quiefcence  of  the  anaftomofing  capillaries  a pale-  ' 
nefs  of  the  fkin  fucceeds,  and  a lefs  fecreticn  of  the  perfpirable 
matter;  from  the  quielcence  of  the  pulmonary  capillaries  a dif-  v 
fculty  of  refpiratiyn  ariles;  and  from  the  quiefcence  of  the 
other  glands  lefs  bile,  lei's  gaftric  and  pancreatic  juice,  are  feciet- 
ed  into  the  ftomach  and  inteftines,  and  lefs  mucus  and  faliva 
are  poured  into  the  mouth  ; whence  ariles  the  dry  tongue,  cof- 
tivenefs,  dry  ulcers,  and  paucity  of  urine.  From  the  quiefcence 
of  the  abforbent  fyftem  arifes  the  great  thirft,  as  left  moifture  is 
abforbed  from  the  atmofphere.  The  abforption  from  the  at- 
mofphere  was  obferved,  by  Dr.  Lyfter,  to  amount  to  eighteen 
ounces  in  one  night,  above  what  he  had  at  the  fame  time  infal- 
libly perfpired.  See  Langrifh.  On  the  fame  account  the  urine 
is  pale,  though  in  fmall  quantity,  for  the  thinner  part  is  not  ab- 
forbed from  it  ; and  when  repeated  ague  fits  continue  long,  the 
legs  fw  ell  from  the  diminiilied.abforption  of  the  cellular  abl'or- 
bents. 


From 


Sect.  XXXII.  9.  DISEASES  OF  IRRITATION.  281 

From  the  quiefcence  of  the  inteflinal  canal  a lofs  of  appetite 
and  flatulencies  proceed.  From  the  partial  quiefcence  of  the 
glandular  vifcera  a fwelling  and  tenfion  about  the  pracordia 
becomes  Rubble  to  the  touch  ; which  is  occafloned  by  the  de- 
lay of  the  fluids  from  the  defect  of  venous  or  lymphatic  abforp- 
tion.  The  pain  of  the  forehead,  and  of  the  limbs,  and  of  the 
fmall  of  the  hack,  arifes  from  the  quiefcence  of  the  membranous 
fafcia,  or  mufcles  of  thofe  parts,  in  the  fame  manner  as  the  Ikin- 
becomes  painful,  when  the  veflels,  of  which,  it  is  compofed,  be- 
come quiefcent  from  cold.  The  trembling  in  confluence  of 
the  pain  of  coldnefs,  the  reftleftnefs,  and  the  yawning,  and 
ftretching  of  the  limbs,  together  with  the  fhuddering,  or  rigours, 
are  convulfive  motions  j.  and  will  be  explained  amongft  the  dil'- 
eafes  of  volition,  SeCt.  XXXIV. 

Sicknefs  and  vomiting  is  a frequent  fymptom  in  the  begin- 
nings of  fever-fits : the  mufcular  fibres  of  the  ftomach  (hare  the 
general  torpor  and  debility  of  the  fyftem ; their  motions  become 
firft  leflened,  and  then  flop,  and  then  become  retrograde]  for 
the  aCt  of  vomiting,  like  the  globus  hyfter-icus  and  the  borbo- 
rigmi  of  hypocondriafis,  is  always  a fymptom  of  debility,  either 
from  want  of  ftimulus,  as  in  hunger ; or  from  want  of  fenforial 
power,  as  after  intoxication ; or  from-  fympathy,  with  feme 
other  torpid  irritative  motions,  as  in  the  cold  fits  of  ague.  See 
Sea.  XII.  5.  5..  XXIX,  1 1. -and  XXXV.  x.  3.  where  this  aft 
of  vomiting  is  further  explained. 

The  final!  pulfe,  which  is  faid  by  fome  writers  to  be  flow  at 
the  commencement  of  ague-fits,  and  which  is  frequently  trem- 
bling and  intermittent,  is  owing  to  the  quiefcence  of  the  heart 
and  arterial  fyftem,  and  to  the  refiftance  oppofed  to  the  circulat- 
ing fluid  from  the  inactivity  of  all  the  glands  and  capillaries. 
The  great  weaknefs  and  inability  to  voluntary  motions,  with 
the  infenftbility  of  the  extremities,  are  owing  to  the  general 
quiefcence  of  the  whole  moving  fyftem ; or,  perhaps,  ftmpiy  to 
the  deficient  production  of  fenforial  power. 

If  all  thefe  fymptoms  are  further  increafed,  the  quiefcence  of 
all  the  mufcles,  including  the  heart  and  arteries,  becomes  com- 
plete, and  death  enfues.  ' This  is  moft  probably  the  cafe  of 
thofe  who  are  ftarved  to  death  with  cold,  and  of  thofe  who  are 
faid  to  die  in  Holland  from  lofig  Ikaiting  on  their  frozen  canals. 

2.  As  foon  as  this  general  quiefcence  of  the  fyftem  ceafes, 
either  by  the  diminution  of  the  caufe,  or  by  the  accumulation  of 
feniorial  power,  (as  in  fyncope,  SeCt.  XII.  7.  1.)  which  is  the 
natural  confequence  of  previous  quiefcence,  the  hot  fit  com- 
mences. Every  gland  of  the  body  is  now  {Emulated  into  ftronger 
aCtion  than  is  natural,  as  its  irritability  is  increafed  bv  accu- 
mulation. 


282  DISEASES  OF  IRRITATION.  Sect.  XXXII.  9 

m illation  of  fenforial  power  during  its  late  quiefcence ; afuper- 
abundance  of  all  the  fecretions  is  produced,  and  an  increafe  of 
heat  in  confequence  of  the  increafe  of  thefe  fecretions.  The  (kin 
becomes  red,  and  the  perfpiration  great,  owing  to  the  increafed 
afition  of  the  capillaries  dining  the  hot  part  of  the  paroxyfm. 
The  fecretion  of  perfpirable  matter  is  perhaps  greater  during 
the  hot  fit  than  in  the  fweating  fit  which  follows ; but  as  the 
abforption  of  it  alfo  is  greater,  it  does  not  ftand  on  the  {kin  in 
vifibie  drops : add  to  this,  that  the  evaporation  of  it  alfo  is  greater, 
from  the  increafed  heat  of  the  {kin.  But  at  the  decline  of  the  hot 
fit,  as  the  mouths  of  the  abforbents  of  the  {kin  are  expofed  to  the 
cooler  air,  or  bed-clothes,  thefe  veffels  fooner  lofe  their  increafed 
activity,  and  ceafe  to  abforb  more  than  their  natural  quantity  : but 
the  fecerning  veffels,  forfome  time  longer,  being  kept  warm  bv 
the  circulating  blood,  continue  to  pourout  anincreafed  quantity 
of  perfpirable  matter,  which  now  hands  on  the  lkin  in  large 
vifibie  drops;  the  exhalation  of  it  alfo  being  leffened  bv  the 
greater  coolnefs  of  the  {kin,  as  well  as  its  abforption  by  tire  di- 
minifhed  adtion  of  the  lymphatics.  See  Clafs  I.  1.  2.  3. 

The  increafed  fecretion  of  biie  and  of  other  fluids  poured  in- 
to the  intefiines  frequently  induces  a purging  at  the  decline  of 
the  hot  fit;  for  as  the  external  abforbent  veffels  have  their 
mouths  expofed  to  the  cold  air,  as  above  mentioned,  they  ceafe  A 
to  he  excited  into  unnatural  activity  fooner  than  the  fecretory 
veffels,  whofe  mouths  are  expofed  to  the  warmth  of  die  blood:  ' 
now,  as  the  internal  abforbents  fyinpathize  with  the  external 
ones,  thefe  alfo,  which  during  the  hot  fit  drank  up  the  thin- 
ner part  of  the  bile,  or  of  other  feci  eted  fluids,  lofe  their  increaf- 
ed activity  before  the  gland  lofes  its  increafed  activity,  at  the  de- 
cline of  the  hot  fit : and  the  loofe  dejections  are  produced  from 
the  fame  caufe,  that  the  increafed  perfpiration  ftands  on  the  iur- 
face  of  the  {kin,  from  the  increafed  abforption  ceaiing  fooner 
than  the  increafed  fecretion. 

The  urine  during  the  cold  fit  is  in  fmall  quantity  and  pale, 
both  from  a deficiency  of  the  fecretion  and  a deficiency  of  the 
abforption.  During  the  hot  fit  it  is  in  its  ufual  quantity,  but 
very  high  coloured  and  turbid,  becaufe  a greater  quantity  had 
been  fecreted  by  the  increafed  action  of  the  kidnies,  and  alio 
a greater  quantity  of  its  more  aqueous  part  had  been  ablorbcu 
from  it  in  the  bladder  by  the  increafed  aefion  of  the  ablorbents; 
and  lafflv,  at  the  decline  of  the  hot  fit  it  is  in  large  quantity  and 
lefs  coloured,  or  turbid,  becaufe  the  abforbent  veffels  of  the 
bladder,  as  obferved  above,  lofe  their  increafed  aefion  bv  Em- 
pathy with  the  cutaneous  ones  fooner  than  the  fecretory  vet- 
ids  of  the  kidnies  lofe  their  increafed  activity.  Hence,  the  quan- 
tity 


Sect.  XXXII.  9.  DISEASES  OF  IRRITATION.  283 

tity  of  the  fediment,  and  the  colour  of  the  urine,  in  fevers,  de- 
pend much  on  the  quantity  fecreted  by  the  kidhies,  and  the 
quantity  abforbed  from  it  again  in  the  bladder : the  kinds  of  fedi- 
ment,  as  the  lateritious,  purulent,  mucous,  or  bloody  fediments, 
depend  on  other  caufes.  It  fhould  be  obferved,  that  if  the 
fweating  be  increafed  by  the  heat  of  the  room,  or  of  the  bed- 
clothes, that  a paucity  of  tuibid  urine  will  continue  to  be  pro- 
duced, as  the  ablorbents  of  the  bladder  will  have  their  adtivity 
increafed  by  their  iympathy  with  tine  veflels  of  the  fkin,  for  the 
purpofe  of  fupplying  the  fluid  expended  in  perfpiration. 

The  pulfe  becomes  flrong  and  full,  owing  to  the  increafed 
irritability  of  the  heart  and  arteries,  from  the  accumulation  of 
fenforial  power  during  their  quiefcence,  and  to  the  quicknefs  of 
the  return  of  the  blood  from  the  various  glands  and  capillaries. 
This  increafed  adtion  of  all  the  fecretory  veflels  does  not  oc- 
cur very  fuddenly;  nor  univerfally  at  the  fame  time.  The 
heat  feems  to  begin  about  the  center,  and  to  be  diffufed  from 
thence  irregularly  to  the  other  parts  of  the  fyftem.  This  may 
be  owing  to  thefituation  of  the  parts  which  firft  became  quie- 
fcent,  and  caufed  the  fever-fit,  efpccially  when  a hardnefs  of 
tumour  about  the  praecordia  can  be  felt  by  the  hand  ; and 
hence  this  part,  in  whatever  vifcus  it  is  feated,  might  be  the 
firft  to  regain  itj  natural  or  increafed  irritability. 

3,  It  muft  be  here  noted,  that  by  the  increafed  quantity  of 
heat,  and  of  the  implufe  of  the  blood,  at  the  commencement  of 
the  hot  fit,  a great  increafe  of  ftimulus  is  induced,  and  is  now- 
added  to  the  increafed  irritability  of  the  fyftem,  which  was  oc- 
cafioned  by  its  previous  quiefcence.  This  additional  ftimulus 
of  heat  and  momentum  of  the  blood,  augments  the  violence  of 
the  movements  of  the  arterial  and  glandular  fyftem  in  an  in- 
creafing  ratio.  Thefe  violent  exertions  ftill  producing  more 
heat  and  greater  momentum  of  the  moving  fluids,  till,  at  length, 
the  fenforial  power  becomes  wafted  by  this  great  ftimulus  be- 
neath its  natural  quantity,  and  predifpofes  the  fyftem  to  a fe- 
cond  cold  fit. 

At  length,  all  thefe  unnatural  exertions  fpontaneoufly  fub- 
fide  with  the  increafed  irritability  that  produced  them;  and 
which  was  itfelf  produced  by  the  preceding  quiefcence,  in  the 
fame  manner  as  the  eye,  on  coming  from  darknefs  into  day- 
light, in  a little  time  ceafes  to  be  dazzled  and  pained,  and  gra- 
dually recovers  its  natural  degree  of  irritability. 

4.  But  if  the  increafe  of  irritability,  and  the  confequent  in- 
creale  of  the  ftimulus  of  heat  and  momentum,  produce  more 
violent  exertions  than  thole  above  defcribed,  great  pain  arifes 
in  fome  part  of  the  moving  fyftem,  as  in  the  membranes  of  the 

P p brain, 


284  DISEASES  OF  IRRITATION.  Sect.  XXXII.  10. 

brain,  pleura,  or  joints;  and  new  motions  of  the  veffels  are 
produced  in  confequence  of  this  pain,  which  are  called  in 
fiammation  ; or  delirium,  or  ftupor  arifes;  as  explained  in 
Se£L  XXL  and  XXXIII.  for  the  immediate  effedb  is  the  fame, 
whether  the  great  energy  of  the  moving  organs  arifes  from  an 
increafe  of  ftimulus,  or  an  increafe  of  irritability  ; though  in 
the  former  cafe  the  wafte  of  fenforial  power  leads  to  debility, 
and  in  the  latter,  to  health. 

Recapitulation. 

X.  Thofe  mufcles,  which  are  lefs  frequently  exerted,  and 
whofeaftions  are  interrupted  by  deep,  acquire  lefs  accumulation 
of  fenforial  power  during  their  quiefcent  ftate,  as  the  mufcles  of 
locomotion.  In  thefe  mufcles,  alter  great  exertion,  that  is,  after 
great  exhauilion  of  fenforial  power,  the  pain  of  fatigue  enfues; 
and  during  reft  there  is  a renovation  of  the  natural  quantity  of 
fenforial  power ; but  where  the  reft,  or  quiefcence  of  the 
mufcle,  is  long  continued,  a quantity  of  fenforial  power  becomes 
accumulated  beyond  what  is  neceffarv;  as  appears  by  the  un- 
eafinefs  occafioned  by  want  of  exercife ; and  which  in  young 
animals  is  one  caufe  exciting  them  into  action,  as  is  feen  in 
the  play  of  puppies  and  kittens. 

But  when  thofe  mufcles,  which  are  habituated  to  perpetual 
aeftion,  as  thofe  of  the  ftomach  by  the  ftimulus  of  food,  thoff* 
of  the  veffels  of  the  fkin  by  the  ftimulus  of  heat,  and  thofe  which.' 
ccnftitute  the  arteries  and  glands  by  the  ftimulus  of  the  blood,.; 
become  for  a time  quiefcent,  from  the  want  of  their  appropri- 
ated ftimuli,  or  by  their  affociations  with  other  quiefcent  parts k 
of  the  fyftem;  a greater  accumulation  of  fenforial  power  is  ac- 
quired during  their  quiefcence,  and  a greater  or  quicker  exhauf- 
tion  of  it  is  produced  during  their  increafed  adlion. 

This  accumulation  of  fenforial  power  from  deficient  adtion, 
if  it  happens  to  the  ftomach  from  want  of  food,  occalicns  the 
pain  of  hunger ; if  it  happens  to  the  veffels  of  the  fkin  from 
want  of  heat,  it  occafions  the  pain  of  cold;  and  if  to  the 
arterial  fyftem  from  the  want  of  its  adapted  ftimuli,  many 
difagreeable  fenfations  are  occafioned,  fuch  as  are  experienced 
in  the  coid  fits  of  intermittent  fevers,  and  are  as  various  as  there 
are  glands  or  membranes  in  the  fyftem,  and  are  generally  term- 
ed univerfal  uneafinefs. 

When  the  quiefcence  of  the  arterial  fyftem  is  not  owing 
to  uefedt  of  ftimulus  as  above,  but  to  the  defective  quantity  of 
fenforial  power,  as  in  the  commencement  of  nervous  fever,  or 
irritative  fever  with  weak  puiie,  a great  torpor  of  this  fyftem  is 
quickly  induced;  becaufe  both  the  irritation  from  the  ftimulus 

of 


Sect.  XXXII.  io.  DISEASES  OF  IRRITATION.  2S5 

of  the  biood,  and  the  aflociation  of  the  vafcular  motions  with 
each  other,  continue  to  excite  the  arteries  into  adtion,  and  thence 
quickly  exhauft  the  ill-fupplied  vafcular  muicles ; for  to  reft  is 
death.;  and  therefore  thofe  vafcular  mufcles  continue  to  proceed, 
though  with  feebler  adtion,  to  the  extreme  of  wearinefs  orfaint- 
nefs ; while  nothing  ftmilar  to  this  affedts  the  locomotive  muf- 
cles, whofe  actions  are  generally  caufed  by  volition,  and  not 
much  fubjedt  either  to  irritation  or  to  other  kinds  of  affociations 
befides  the  voluntary  ones,  except  indeed  when  they  are  excited 
by  the  lafh  of  flavery. 

In  thefe  vafcular  mufcles,  which  are  fubjedt  to  perpetual  ac- 
tion, and  thence  liable  to  great  accumulation  of  fenforial  power 
during  their  quiefcence  from  want  of  ftimulus,  a great  increafe 
of  activity  occurs,  either  from  the  renewal  of  their  accuftomed 
ftimulus,  or  even  from  much  lets  quantities  of  ftimulus  than  ufual. 
This  increafe  of  adtion  conftitutes  the  hot  fit  of  fever,  which 
•is  attended  with  various  increafed  fecretions,  with  great  conco- 
mitant heat,  and  general  uneafinefs.  The  uneafinefs  attending 
this  hot  paroxyfm  of  fever,  or  fit  of  exertion,  is  very  different 
from  that  which  attends  the  previous  cold  fit,  or  fit  of  quie- 
fcence, and  is  frequently  the  caufe  of  inflammation,  as  in  pleurify, 
which  is  treated  of  in  the  next  fedtion. 

A fimilar  effedt  occurs  after  the  quiefcence  of  our  organs  of 
fenfe ; thofe  which  are  not  fubjedt  to  perpetual  adtion,  as  the 
tafte  and  fmeil,  are  lefs  liable  to  an  exuberant  accumulation  of 
fenforial  power  after  their  having  for  a time  been  inadtive  ; but 
the  eye,  which  is  in  perpetual  adtion  during  the  day,  becomes 
dazzled,  and  liable  to  inflammation  after  a temporary  quiefcence. 

Where  the  previous  quiefcence  has  been  owing  to  a defect 
of  fenforial  power,  and  not  to  a defedt  of  ftimulus,  as  in  the  irri- 
tative fever  with  weak  pulfe,  a fimilar  increafe  of  activity  of 
the  arterial  fyftem  fucceeds,  either  from  the  ufual  ftimulus  of  the 
blood,  or  from  a ftimulus  leis  than  ufual;  but  as  there  is,  in 
general,  in  thefe  cafes  ot  fever  with  weak  pulfe,  a deficiency  of 
the  quantity  of  the  blood,  the  pulle  in  the  hot  fit  is  weaker  than 
in  health,  though  it  is  ftronger  than  in  the  cold  fit,  as  explained 
in  No.  2.  of  this  fedtion.  But  at  the  fame  time,  in  thofe  fevers 
where  the  defedt  of  irritation  is  owing  to  the  defedt  of  the  quan- 
tity of  fenforial  power,  as  well  as  to  the  defect  of  ftimulus,  ano- 
ther circumftance  occurs,  which  coniifts  in  the  partial  diftribu- 
tion  of  it,  as  appears  in  partial  flufhings,  as  of  the  face  or  bofom, 
•while  the  extremities  are  cold;  and  in  the  increafe  of  particular 
fecretions,  as  of  bile,  faliva,  infenfible  perfpiration,  with  great 
heat  of  the  fkin,  or  with  partial  fweats,  or  diarrhoea. 

There  are  alio  many  uneaiy  fenfations  attending  thefe  increaf- 
ed 


286  DISEASES  OF  SENSATION.  Sect.  XXXIII. 


ed  actions,  which.  like  thofe  belonging  to  thehot  fit  of  fever  with 
ftrong  pulfe,  are  frequently  followed  by  inflammation,  as  in 
fcarlet  fever  ; which  inflammation  is  neverthelefs  accompanied 
with  a pulfe  weaker,  though  quicker,  than  the  pulfe  during  the 
remifiion  or  intermiflion  of  the  paroxyfms,  though  ftronger  than 
that  of  the  previous  cold  fit. 

From  hence  I conclude,  that  both  the  cold  and  hot  fits  of 
fever  are  neceflfary  conlequences  of  the  perpetual  and  incelT;  nt 
aCtion  of  the  arterial  and  glandular  fyftem  ; fince  thofe  mui  - 
cular  fibres  and  thofe  organs  of  fenfe,  which  are  moft  frequenrlv 
exerted,  become  necelTarily  moft  affeCted  both  with  defect  and 
accumulation  of  fenforial  power  : and  that  hence  fever-fits  are 
not  an  effort  of  nature  to  relieve  herfclf,  and  that  therefore 
they  fhould  always  be  prevented  or  diminifhed  as  much  as  pof- 
iible,  by  any  means  which  decreafe  the  general  or  partial  vaf- 
cuiar  actions  when  they  are  greater,  or  bv  increaling  them 
when  they  are  lei's  than  in  health,  as  deferibed  in  SeCt.  Xll.  6.  I. 

Thus  have  I endeavoured  to  explain,  and  I hope  to  the  ia- 
tisfaCtion  of  the  candid  and  patient  reader,  the  principal  iymp- 
toms  or  circumftances  of  fever,  without  the  introduction  of  the 
fupernatural  power  of  fpafm.  To  the  arguments  in  favour  ot 
the  doCtrine  of  fpafm  it  may  be  lufficient  to  reply,  that  in  the 
evolution  of  medical  as  well  as  of  dramatic  cataftrophe, 

Nec  Deus  intersit.  nisi  dignus  vindice  nodus  inciderit. 

Hor.  1 


SECT.  XXXIII. 

DISEASES  OF  SENSATION. 

I.  I.  Motions  excited  by  fenfation.  Digeflion.  Generation, 
Pleafure  of  exifience.  Hypochondmacijm.  2.  Pain  in- 
troduced. Senfitive  fevers  of  two  kinds.  3.  Twofenfthk 

rial  pozvers  exerted  in  fenfitive  fevers.  Size  of  the  blood. 
IN ervous fevers  dijlinguijhed from  putrid  ones.  The  fcp-. 
tic  and  antifeptic  theory.  4.  Tjjo  kinds  of  delirium.  5. 
Other  animals  are  lefs  liable  to  delirium,  cannot  receive 
our  contagious  difeafes,  and  arc  lefs  liable  to  madnefs.  II. 
1.  Senfitive  motions  generated.  2.  Inflammation  explain- 
ed. 3.  Its  remote  cau/es from  excefs  of  irritation,  or  of 
irritability,  not  from  thofe  pains  ■ which  are  owing  to  de- 
feft  of  irritation.  New  vcjfels  produced,  and  much  heat. 
4.  Purulent  matter  fecreted.  5.  Contagion  explain'd. 
6.  Received  but  once.  7.  If  common  matter  be  contagion s P 
8,  Why  feme  contagions  are  received  but  nice.  9.  1 1 by 


Sect.  XXXIII.  i.  DISEASES  OF  SENSATION.  287 

others  may  he  received  frequently.  Contagions  of  finall- 
pox  and  meajles  do  not  aft  at  the  fame  time.  Two  cafes 
of  fuch  patients,  io.  The  blood  from  patients  in  the  fmall- 
pox  will  not  infebl  others.  Cafes  of  children  thus  inocu- 
lated. The  variolous  contagion  is  not  received  into  the 
blood.  It  adts  by  fenfitive  affociation  between  the  fomach 
and  Jkin.  III.  I.  Abforption  of  folds  and  fluids.  2.  Art 
of  healing  ulcers.  3.  Mortification  attended  with  lefs 
pain  in  weak  people. 

T.  1.  AS  manv  motions  of  the  body  are  excited  and  continu- 
ed by  irritations,  lb  others  require,  either  conjundtly  with  thefe 
or  feparateiy,  the  pleafureabie  or  painful  fenfations,  for  the  pur- 
pofe  of  producing  them  with  due  energy.  Among!!  thefe  the 
bufmefs  of  digeftion  fupplies  us  with  an  inftance:  if  the  food 
which  we  fwallow  is  not  attended  with  agreeable  fenfation,  it 
digefts  lefs  perfedtly ; and  if  very  difagreeable  fenfation  accom- 
panies it,  fuch  as  a naufeous  idea,  or  very  difguftful  tafte,  the 
digeftion  becomes  impeded;  or  retrograde  motions  of  the  fto- 
mach  and  oefophagus  fucceed,  and  the  food  is  ejedled. 

The  bufmefs  of  generation  depends  fo  much  on  agreeable 
fenfation,  that,  where  the  objecl  is  difguftful,  neither  voluntary 
exertion  nor  irritation  can  erFedt  the  purpofe ; which  is  alfo  lia- 
ble tn  be  interrupted  by  the  pain  of  fear  or  bafhfulnefs. 

Be'ides  the  pleafure  which  attends  the  irritations  produced  by 
the  objedls  of  luft  and  hunger,  there  feems  to  be  a fum  of  plea- 
fureabie affedtion,  accompanying  the  various  fecretions  of  the 
numerous  glands,  which  conftitutes  the  pleafure  of  life,  in  con- 
tradiftindlion  to  the  tedium  vitae.  This  quantity,  or  fum  of 
pleafureabie  afFedlion,  feems  to  contribute  to  the  due  or  energetic 
performance  of  the  whole  moveable  fyftem,  as  well  that  of  the 
heart  and  arteries,  as  of  digeftion  and  of  abforption  ; fince,  with- 
out the  due  quantity  of  pleafureabie  fenfation,  flatulency  and 
hypochondriacifm  afFedt  the  inteftines,  and  a languor  feizes  the 
arterial  pulfations  and  fecretions;  as  occurs  in  great  and  con- 
tinued anxiety  of  the  mind. 

2,  Befides  the  febrile  motions  occaftoned  by  irritation,  de- 
feribedin  Sedl.  XXXII.  and  termed  irritative  fever,  it  frequent- 
ly happens  that  pain  is  excited  by  the  violence  of  the  fibrous 
contradlions ; and  other  new  motions  are  then  luperadded,  in 
confequence  of  fenfation,  which  we  fliall  term  febris  fenfitiva, 
or  fenfitive  fever..  It  muft  be  obferved,  that  moft  irritative  fe- 
vers begin  with  a decreafea  exertion  of  irritation,  owing  to  de- 
fed!  of  ftimulus ; but  that,  on  the  contrary,  the  fenfitive  fevers, 
or  inflammations,  generally  begin  with  the  increafed  exertion 


s88  DISEASES  OF  SENSATION.  Sect.  XXXIII.  i. 


of  fenfation,  as  mentioned  in  Se£t.  XXXI.  on  temperaments : 
for  though  the  cold  fit,  which  introduces  inflammation,  com- 
mences with  decreafed  irritation,  yet  the  inflammation  itfelf 
commences  in  the  hot  fit  during  the  increafe  of  fenfation. 
Thus  a common  puftuie,  or  phlegmon,  in  a part  of  little  fallibi- 
lity, does  not  excite  an  inflammatory  fever ; but  if  the  ftomach, 
inteftines,  or  the  tender  fubftance  beneath  the  nails,  be  injured, 
great  fenfation  is  produced,  and  the  whole  fvftem  is  thrown 
into  that  kind  of  exertion  which  conllitutes  inflammation. 

Thefe  fenfitive  fevers,  like  the  irritative  ones,  refoive  thent- 
felves  into  thofe  with  arterial  ftrength,  and  thofe  with  arterial 
debility ; that  is,  with  excefs  or  defect  of  fenforial  power : thefe 
may  be  termed  the  febris  fenfitiva  pulfu  forti,  fenfitive  fever  with 
ftrong  pulfe,  which  is  the  fynocha,  nr  inflammatory  fever;  and 
the  febris  fenfitiva  pulfu  debili,  fenfitive  fever  w'ith  weak  pulfe, 
which  is  the  typhus  gravior,  or  putrid  fever  of  fome  writers. 

3.  The  inflammatory  fevers,  which  arc  here  termed  fenfitive 
fevers  with  ftrong  pulfe,  are  generally  attended  with  fome  topi- 
cal inflammation,  as  pleurifv,  peripneumonv,  or  rheumatlfm, 
which  diftinguifhes  them  from  irritative  fevers  with  ftrong  pulfe. 
The  pulfe  is  ftrong,  quick,  and  full;  for  in  this  fever  there  is 
great  irritation,  as  well  as  great  fenfation,  employed  in  moving 
the  arterial  fvftem.  The  lize,  or  coagulable  ivmph,  which  ap- 
pears on  the  blood,  is  probably  an  increafed  fecretion  from  die 
inflamed  internal  lining  of  the  whole  arterial  fyftem,  the  thinner 
part  being  taken  away  by  the  increafed  ablorpticm  of  the  in- 
flamed lymphatics. 

The  fenfitive  fevers  with  weak  pulfe,  which  are  termed  pu- 
trid or  malignant  fevers,  are  dillinguifhed  from  irritative  fevers 
with  weak  pulfe,  called  nervous  fevers,  deferibed  in  the  laft  lec- 
tion, as  the  former  coniifts  of  inflammation  joined  with  dcbiiitv, 
and  the  latter  of  debility  alone.  Hence  there  is  greater  heat 
and  more  florid  colour  of  the  fkin  in  the  former,  with  petechias, 
or  purple  fpots,  and  a pin  re,  or  Houghs  in  the  throat,  and  gene- 
rally with  pievious  contagion. 

When  animal  matter  dies,  as  a flough  in  the  throat,  or  the 
mortified  part  of  a carhunkle,  if  it  be  kept  moift  and  warm,  as 
during  its  adhefion  to  a living  body,  it  will  foon  putrify.  This, 
and  the  origin  of  contagion,  front  putrid  animal  fubftances,  feein 
to  have  given  rile  to  the  ieptic  and  antileptic  dteory  of  diele 
fevers. 

The  matter  in  puftules  and  ulcers  is  thus  liable  to  become 
putrid,  and  to  produce  microfcopic  animalcula ; the  urine,  if 
too  long  retained,  may  alio  gain  a putrefeent  fmeil,  as  well  as 
die  alvine  feces ; but  fome  writers  have  gone  fo  far  as  to  be- 
lieve, 


Sect.  XXXIII.  r.  DISEASES  OF  SENSATION.  289 

lieve,  that  the  blood  itfelf  in  thefe  fevers  has  fmelt  putrid, 
when  drawn  from  the  arm  of  the  patient:  hut  this  feems  not 
well  founded;  iince  a Angle  particle  of  putrid  matter  taken  into- 
the  blood  can  produce  fever,  how  can  we  conceive  that  the 
whole  mafs  could  continue  a minute  in  a putrid  ftate  without 
deftroying  life  ? Add  to  this,  that  putrid  animal  fubfrances  give 
up  air,  as  in  gangrenes  ; and  that  hence,  if  the  blood  was  putrid, 
air  fhoujd.be  given  out,  which,  in  the  blood  velTels  is  known 
to  occafion  immediate  death. 

In  thefe  fenfitive  fevers  with  flrong  pulfe,  (or  inflamma- 
tions) there  are  too  fenforial  faculties  concerned  in  producing 
the  difeafe,  viz.  irritation  and  fenfation;  and  hence,  as  their 
combined  acftion  is  more  violent,  the  general  quantity  of  fen- 
forial power  becomes  further  exhaufted  during  the  exacerba- 
tion, and  the  fyftetn  more  rapidly  weakened  than  in  irritative 
fever  with  flrong  pulfe ; where  the  fpirit  of  animation  is  weak- 
ened by  but  one  mode  of  its  exertion : fo  that  this  febris  fenlitiva 
pulfu  ftirti  (or  inflammatory  fever,)  may  be  confidered  as  the 
febris  irritativa  pulfu  forti,  with  the  addition  of  inflammation; 
and  the  febris  fenfltiva  pulfu  debili  (or  malignant  fever)  may 
be  coniidered  as  the  febris  irritativa  pulfu  debili,  (or  nervous 
fever,)  with  the  addition  of  inflammation. 

4.  In  thefe  putrid  or  malignant  fevers  a deficiency  of  irrita- 
bility accompanies  the  increafe  of  fenflbility;  and  by  this  wafte 
of  fenforial  power  by  the  excefs  of  fenfation,  which  was  al- 
ready too  frnall,  arifesthe  delirium  and  ftupor  which  fo  perpe- 
tually attend  thefe  inflammatory  fevers  with  arterial  debility. 
In  thefe  cafes,  the  voluntary  power  firft  ceafes  to  aft  from 
deficiency  of  fenforial  fpirit ; and  the  ftimuli  from  external  bo- 
dies have  no  effeft  on  the  exhaufted  fenforial  power,  and  a de- 
lirium like  a dream  is  the  confequence.  At  length,  the  inter- 
nal ftimuli  ceafe  to  excite  fufficient  irritation,  and  the  fecretions 
are  either  not  produced  at  all,  or  two  parfimonious  in  quantity. 
Amongft  thefe,  the  fecretion  of  the  brain,  or  production  of  the 
fenforial  power,  becomes  deficient,  till  at  laft  all  fenforial 
power  ceafes,  except  what  is  juft  neceflary  to  perform  the  vital 
motions,  and  a ftupor  fucceeds;  which  is  thus  owing  to  the 
fame  caufe  as  the  preceding  delirium  exerted  in  a greater  degree. 

This  kind  of  deliiium  is  owing  to  a fufpenfion  of  volition, 
and  to  the  difobedience  of  the  fenfes  to  external  ftimuli,  and  is 
always  occalioned  by  great  debility,  or  paucity  of  fenforial 
power ; it  is  therefore  a bad  fign  at  the  end  of  inflammatory 
fevers,  which  had  previous  arterial  ftrength,  as  rheumatifm  or 
pleurify,  as  it  iliews  the  prefence  of  great  exhauftion  of  fenforial 
power  in  a fyftem,  which  having  lately  been  expofed  to  great 

excitement. 


290  DISEASES  OF  SENSATION.  Sect.  XXXIII.  i. 

excitement,  is  not  fo  liable  to  be  ftimulated  into  its  healthy  ac- 
tion, either  by  additional  ftimulus  of  food  and  medicines,  or  by 
the  accumulation  of  fenforial  power  during  its  prefent  torpor. 
In  inflammatory  fevers  with  debility,  as  thofe  termed  putrid  fe- 
vers, delirium  is  fometimes,  as  well  as  ftupor,  rather  a favour- 
able ftgn;  as  lefs  fenforial  power  is  wafted  during  its  continu- 
ance (fee  Clals  II.  i.  6.  8.)  ; and  the  conftitution  not  having 
been  previoufly  expofed  to  excels  of  ftimulation,  is  more  liable 
to  be  excited  after  previous  quiefcence. 

When  the  fum  ot  general  pleafureable  fenfation  becomes  too 
great,  another  kind  of  delirium  fupervenes,  and  the  ideas  thus 
excited  are  miftaken  for  the  irritations  of  external  objects : Inch 
q delirium  is  produced  for  a time  by  intoxicating  drugs,  as  fer- 
mented liquors,  or  opium:  a permanent  delirium  of  this  kind  is 
fometimes  induced  by  the  pleafures  ot  inordinate  vanity,  or  by 
the  enthufiaftic  hopes  of  heaven.  In  thefe  cafes,  the  power  of 
volition  is  incapable  of  exertion,  and  in  a great  degree,  the  ex- 
ternal fenfes  become  incapable  of  perceiving  their  adapted  fti- 
muli,  becaufe  the  whole  fenforial  power  is  employed  or  ex- 
pended on  the  ideas  excited  by  pleafureable  tenfatiorr.  . 

This  kind  of  delirium  is  diftinguifhed  from  that  which  at- 
tends the  fevers  above  mentioned,  from  its  not  being  accom- 
panied with  general  debility,  but  ftrnply  with  excels  of  plea- 
fureable  fenfation ; and  is,  therefore,  in  fome  mealure,  allied 
to  madnefs  or  to  reverie : it  differs  from  the  delirium  ot  dreams, 
as  in  this  the  power  of  volition  is  not  totally  fufpended,  nor 
are  the  fenies  precluded  from  external  ftimulation  ; there  is, 
therefore,  a degree  of  conftftency  in  this  kind  of  delirium,  and 
a degree  of  attention  to  external  objedts,  neither  of  which  exift 
in  the  delirium  of  fevers  or  in  dreams. 

5.  It  would  appear,  that  the  vafcular  fvftems  of  other  animals 
are  lefs  liable  to  be  put  into  adfion  by  their  general  fum  ot  plea- 
fureable or  painful  fenfation ; and  that  the  trains  of  their  ideas, 
and  the  mufcular  motions  ufually  aft'ociated  with  them,  are  lefs 
powerfully  connected  than  in  the  human  fyftem.  For  ochtr 
animals  neither  w;eep,  nor  fmile,  nor  laugh;  and  are  hence 
feldom  fuhjedf  to  delirium,  as  treated  of  in  Se£i.  XVI.  on  In- 
ftindt.  Now,  as  our  epidemic  and  contagious  difeates  are  pro- 
bably produced  by  difagreeable  fenfation,  and  not  limply  by  ir- 
ritation, there  appears  a reafon  w hy  brute  animals  are  lets  liable 
to  epidemic  or  contagious  dileafes ; and  fecondly,  why  none 
of  our  contagions,  as  the  fmall-pox  or  meazies,  can  be  commu- 
nicated to  them,  though  one  ot  theirs,  viz.  the  hydrophobia,  as 
well  as  many  ot  their  poifons,  as  thofe  ot  tnakes  and  ot  imedts, 
communicate  their  deleterious  or  painful  effects  to  mankind. 

Where 


Sect. XXXIII. i.  DISEASES  OF  SENSATION.  292 

Where  the  quantity  of  general  painful  fenfation  is  too  great 
in  the  fvftem,  inordinate  voluntary  exertions  are  produced  either 
of  out  ideas,  as  in  melancholy  and  madnefs,  or  of  oui  mufcles,  as 
in  convullion.  From  thefe  maladies  alfo  brute  animals-are  much 
more  exempt  than  mankind,  owing  to  their  greater  inaptitude  to 
voluntary  exertion,  as  mentioned  in  Se£t.  XVI.  on  Inftindt. 

II.  i.  When  any  moving  organ  is  excited  into  fuch  violent 
motions,  that  a quantity  of  plealureable  or  painful  fenfation  is 
produced,  it  irequently  happens  (but  not  always)  that  new  mo- 
tions of  the  affected  organ  are  generated  in  confequence  of  the 
pain  or  plealure,  which  are  termed  inflammation. 

Thefe  new  motions  are  of  a peculiar  kind,  tending  to  diftend 
the  old,  and  to  produce  new  fibres,  and  thence  to  elongate  the 
ftraight  mufcles,  which  ferve  locomotion,  and  to  form  new 
veffeis  at  the  extremities  or  Tides  of  the  vafcular  mufcles. 

2.  Thus  the  pleafureable  fenfations  produce  an  enlargement 
of  the  nipples  of  nurfes,  of  the  pallas  of  the  tongue,  of  the  penis, 
and  probably  produce  the  growth  ot  the  body  from  its  embryon 
ffate  to  its  maturity ; whilft  the  new  motions,  in  confequence 
of  painful  fenfation,  with  the  growth  of  the  fibres  or  veffeis, 
which  they  occafion,  are  termed  inflammation. 

Hence,  when  the  ftraight  mufcles  are  inflamed,  part  of  their 
tendons  at  each  extremity  gain  new  life  and  fenfibjlity,  and 
thus  the  mufcle  is  for  a time  elongated  ; and  the  inflamed  bones 
become  foft,  vafcular,  and  fenfible.  Thus,  new  veffeis  fhoot 
over  the  cornea  of  inflamed  eyes,  and  into  fchirrous  tumours, 
when  they  become  inflamed  : and  hence,  all  inflamed  parts 
grow  together  by  intermixture,  and  inofculation  of  the  new 
and  old  veffeis. 

The  heat  is  occafioned  from  the  increafed  fecretions  either 
of  mucus,  or  of  the  fibres,  which  produce  or  elongate  the  vef- 
feis. The  red  colour  is  owing  to  the  pellucidity  of  the  newly 
formed  veffeis,  as  the  arterial  parts  of  them  are  probably  formed 
before  their  correfpondent  venous  parts. 

3.  Thefe  new  motions  are  excited  either  from  the  increafed 
quantity  of  fenfation,  in  confequence  of  greater  fibrous  con- 
tra dlions,  or  from  increafed  fenfibility,  that  is,  from  the  increafed 
quantity  ot  fenforial  power  in  the  moving  organ.  Hence  they 
are  induced  by  great  external  ftimuii,  as  by  wounds,  broken 
bones  ; and  by  acrid  or  infectious  materials  ; or  by  common 
Ftimuii  on  thofe  organs  which  have  been  fome  time  quiefeent; 
as  the  ufuul  light  of  the  day  inflames  the  eyes  of  thofe  who 
have  been  confined  in  dungeons,  and  the  warmth  of  a com- 
mon fire  inflames  thofe  who  have  been  previoufly  expofed  to 
much  cold. 

Q q 


But 


292  DISEASES  OF  SENSATION!  Sect.  XXXIII.  2'. 

Butthefe  new  motions  are  never  generated  by  that  pain  which 
arifes  from  defect  of  ftimulus,  as  from  hunger,  .thirft,  cold,  01 
inanition,  with  all  thofe  pains  which  are  termed  nervous. 
Where  thefe  pains  exift,  the  motions  of  the  affected  part  are 
leffened ; and  if  inflammation  fucceeds,  it  is  infomediftant  part; ; 
as  coughs  are  cauled  by  coldnefs  and  moifture  being  long  ap- 
plied to  the  feet ; or,  it  is  in  confequence  of  the  renewal  of  the 
ftimulus,  as  of  heat  or  food,  which  excites  our  organs  into 
ftronger  action  after  their  temporary  quiefcence;  as  kibed  heels 
after  walking  in  Inow. 

4.  But  when  thefe  new  modons-of  the  vafcular  mufcles  are 
exerted  with  greater  violence,  and  thefe  veftels  are  either  elon- 
gated too  much  or  too  haftily,  a new  material  is  fecreted  lrom 
their  extremities,  which  is  of  various  kinds,  according  to  the 
peculiar  animal  motions  of  this  new  kind  of  gland,  which  fe- 
cretes  it  ; fuch-is  tire. pus  laudahile,  of  common  matter,  the  va- 
riolous matter,  venereal  matter,  catarrhous  matter,  and  many 
others. 

5.  Thefe  matters  are  the  product  of  an  animal  procefs : 
■they  are  fecreted  or  produced  from  the  blood  by  certain  difeal- 
ed  motions  of  the  extremities  of  the  blood-veffels,  and  are,  on 
that  account,  all  of  them  contagious ; for  if  a portion  cf  any 
cf  thele  matters  is  tranfmitted  into  the  circulation,  or  perhaps 
only  inlei  ted  into  the  fkin,  or  beneath  the  cuticle  of  an  healthy 
perron,  its  ftimulus,  in  a certain  time,  produces  the  lame  kind 
of  morbid  motions  by  which  itfelf  was  produced  ; and  hence  a 
fimilar  matter  is  generated.  See  Se£t.  XXXIX.  6.  x. 

6.  I-t  is  remarkable,  that  many  of  thele  contagious  matters 
are  capable  of  producing  a fimilar  difeafe  but  once,  as  the 
finall-pox  and  mealies ; and  I fuppofe  this  is  true  of  all  thofe 
contagious  difeafes  which  are  fpontaneoufly  cured  by  nature  in 
a certain  time ; tor  if  the  body  was  capabie  of  receiving  the  dif- 
eafe a fecond  time,  the  patient  inuft  perpetually  infedt  him!  elf 
by  the  very  matter  which  he  has  hinrfelf  produced,  and  is  lodged 
about  him  ; and  hence  he  could  never  become  tree  from  the  ciii"- 
eafe.  Something  fimilar  to  this  is  leen  in  the  fecondary  fever 
of  the  confluent  imall-pox : there  is  a great  abforption  of  vario- 
lous matter,  a verv  minute  part  of  which  would  give  the  genuine 
fmall-pox  to  another  perion  ; hut  here  it  only  Simulates  the  ivl- 
tein  into  00114x1011  fever,  like  that  which  common  pas,  or  any 
other  acrid  material  might  occaiion. 

7.  In  the  pulmonary  coni umption,  where  common  mattci  is 
daily  abforbed,  an  irritative  fever  only,  not  an  inflammatory 
one,  is  produced;  which  is  terminated  like  other  irritative 
vers,  by  lweats  or  loofe  ftools.  Hence  it  does  not  appear,  that 

tins 


■Sect.  XXXIII.  a.  DISEASES  OF  SENSATION.  293 

this  abforbed  matter  always  a£ls  as  a contagious  material,  pro- 
ducing frefh  imlaimnation  or  new  abfcefTes.  Though  there  is 
reafon  to  believe,  that  the  firft  time  any  common  matter  is  ab- 
forbed, it  has  this  effedl,  but  not  the  fecond  time,  like  the  va- 
riolous matter  above  mentioned. 

This  accounts  for  the  opinion  that  the  pulmonary  confump- 
tion  is  fometimes  infectious,  wiiich  opinion  was  held  by  the  an- 
cients, and  continues  in  Italy  at  prefent;  and  I have  myfeir  feen 
three  or  four  inftances,  where  a hufband  and  wife,  who  have 
fjept  together,  and  have  thus  much  received  each  other’s  breath, 
who  have  infedted  each  other,  and  both  died  in  confequence  of 
the  original  taint  of  only  one  of  them.  This  alfo  accounts  for 
die  abfcefTes  in  various  parts  of  the  body,  that  are  fometimes 
•produced  after  the  inoculated  fmall-pox  is  terminated  ; for  this 
fecond  abforption  of  variolous  matter  adds  like  common  matter, 
and  produces  only  irritative  fever  in  thofe  children  whofe  con- 
ftitutions  have  already  experienced  the  abforption  of  common 
matter;  and  inflammation,  with- a tendency  to  produce  new 
abfcefTes  in  thofe  whofe  conflitutions  have  not-experienced  the 
abforpdons  of  common  matter. 

It  is  probable,  that  more  certain  proofs  might  have  been 
found  to  drew,  that  common  matter  is  infeftions  the  firft  time 
it  is  abforbed,  tending  to  produce  funilar  abfcefTes,  but  not  the 
fecond  time  of  its  abforption,  if  this  fubject  had  been  attended  to. 

8.  Thefe  contagious  difeafes  are  very  numerous,  as  the  plague, 
fmall-pox,  chicken-pox,  mealies,  fearlet-fever,  pemphigus,  ca- 
tarrh, chincough,  venereal  difeafe,  itch,  trichoma,  tinea.  The 
infectious  material  does  not  feem  to  be  dififolved  by  the  air,  but 
only  mixed  with  it  perhaps  in  fine  powder,  which  foon  Tubiides  ; 
lince  many  of  thefe  contagions  can  only  be  received  by  adtual 
contaCt;  and  others  of  them  only  at  fmall  diftances  from  the 
infeCted  perfon;  as  is  evident  from  many  perfons  having  been 
near  patients  of  the  fmall-pox  without  acquiring  the  difeafe. 

The  reafou  why  many  of  thefe  diieales  are  received  but 
once,  and  others  repeatedly,  is  not  well  underftood  ; it  appears 
to  me,  that  tire  conftitution  becomes  fo  accuftomed  to  the  ftimuli 
of  thefe  infectious  materials,  by  having  once  experienced  them, 
that  though  irritative  motions,  as  hectic  fevers,  may  again  be 
produced  by  them,  yet  no  fenfation,  and  in  confequence  no  ge- 
neral inflammation  fucceeds ; as  difagreeabie  fmeils  or  taftes  by 
habit  ceafe  to  be  perceived;  they  continue  indeed  to  excite  irri- 
tative ideas  on  the  organs  of  fenfe,  but  thefe  are  not  fucceeded 
•by  fenfation. 

There  are  many  irritative  motions,  which  were  at  firft  fuc- 
ceeded by  fenfation,  but  which  by  frequent  repetition  ceafe  to  ex- 
cite 


394  DISEASES  OF  SENSATION.  Sect.  XXXIII.  2. 

cite  fenfation|  as  explained  in  Sedd.  XX.  on  Vertigo.  And  that 
this  circumftance  exifts  in  refpedt  to  infectious  matter  appears 
from  a known  fact;  that  nurles,  who  have  had  the  fmall-pox, 
are  liable  to  experience  frnall  ulcers  on  their  arms  bv  the  contact 
of  variolous  matter  in  lifting  their  patients;  and  that  when  pa- 
tients, who  have  formerly  had  the  lmall-pox,  have  been  inocu- 
lated in  the  arm,  a phlegmon,  or  inflamed  fore,  has  fucceeded. 
but  no  fubfequent  fever.  Which  fhews,  that  the  contagions 
matter  of  the  fmall-pox  has  not  lolt  its  power  of  ftimulating  tb.e 
part  it  is  applied  to,  but  that  the  general  fvfdem  is  not  affected 
in  confequence.  See  Seddion  XII.  7.  6.  XIX.  10. 

9.  From  the  accounts  of  the  plague,  virulent  catarrh,  and  pu- 
trid dyfentery,  it  feems  uncertain  whether  thefe  difeafesare  ex- 
perienced more  than  once;  but  the  venereal  dileafe  and  itch  arc 
doubtlefs  repeatedly  infectious ; and  as  thefe  difeafes  are  never 
cured  fpontaneoufly,  but  require  medicines,  which  add  without 
apparent  operation,  fome  have  fufpected,  that  the  contagious 
material  produces  fimilar  matter  rather  by  a chemical  chance  of 
tiie  fluids,  than  by  an  animal  procefs ; and  that  the  fpecific 
medicines  deflroy  their  virus  by  chemically  combining  with  it. 
This  opinion  is  fuccefsfully  combated  by  Air.  Hunter,  in  hi:. 
Treatife  on  Venereal  Dileafe,  Part  I.  c.  i. 

But  this  opinion  wants  the  fupport  of  analogy,  as  there  is  no 
known  procefs  in  animal  bodies,  which  is  purely  chemical,  not 
even  digeftion  ; nor  can  any  of  thefe  matters  be  produced  by 
chemical  procefles.  Add  to  this,  that  it  is  probable  that  the 
infedds  obferved  in  the  puflules  of  the  itch,  and  in  the  {fools  of 
dyfenteric  patients,  are  the  confequences,  and  not  the  caufes  of 
thefe  difeafes.  And  that  the  fpeciflc  medicines,  which  cure 
the  itch  and  lues  venerea,  as  brimflone  and  mercury,  add  only 
by  increaflng  the  abforption  of  the  matter  in  the  ulcufcles  of 
thofe  difeafes,  and  thence  difpoflng  them  to  heal,  which  would 
otherwife  continue  to  tpread. 

Why  the  venereal  dileate,  and  itch,  and  tenia,  or  fealdhead, 
arc  repeatedly  contagious,  while  thole  contagions,  attended  with 
fever,  can  be  received  but  once,  feems  to  depend  on  their  being 
rather  local  difeafes  than  univerfal  ones,  and  are  hence  not  at- 
tended with  fever,  except  the  purulent  fever  in  their  laid  ftages. 
when  the  patient  is  defdroyed  bv  them.  On  this  account  the 
whole  of  the  ivflem  does  not  become  habituated  to  thefe  morbid 
adtions,  lo  as  to  ceale  to  be  affedded  with  fenfation,  by  a repe- 
tition of  the  contagion.  Thus  the  contagious  matter  ot  the  ve- 
nereal difeafe,  and  ot  the  tenia,  aif'edds  the  lymphatic  glands,  as 
the  inquinal  glands,  and  thofe  about  the  roots  ot  the  hair  and 
neck,  where  it  is  arrelded,  but  does  not  feetn  to  affedd  the  biood- 
veifels,  lmce  no  fever  endues. 

Hence 


Sect.  XXXIII.  2.  DISEASES  OF  SENSATION.  295 

Hence  it  would  appear,  that  thefe  kinds  of  contagion  are  pro- 
pagated not  by  means  of  the  circulation,  but  by  fympathy  of  dis- 
tant parts  with  each  other;  fince,  if  a diftant  part,  as  the  palate, 
fliould  be  excited  by  fenfitive  aflbciation  into  the  fame  kind  of 
motions  as  the  parts  originally  affedted  by  the  contact  of  in- 
fectious matter,  that  diftant  part  will  produce  the  fame  kind  of 
infedtious  matter;  for  every  fecretion  from  the  blood  is  formed 
from  it  by  the  peculiar  motions  of  the  fine  extremities  of  the 
gland  which  fecretes  it;  the  various  fecreted  fluids,  as  the  bile, 
faliva,  gaftric  juice,  not  previoufly  exifting,  as  fuch,  in  the 
blood-veflels. 

And  this  peculiar  fympathy  between  the  genitals  and  the 
throat,  owing  to  fenfitive  affbciation,  appears  not  only  in  the 
production  of  venereal  ulcers  in  the  throat,  but  in  variety  of  other 
inftances,  as  in  the  mumps,  in  the  hydrophobia,  fome  coughs, 
ftrangulation,  the  production  of  the  beard,  change  of  voice  at 
puberty.  Which  are  further  defcribed  inClafs  IV.  2.  1.  7. 

To  evince  that  the  production  of  fuch  large  quantities  of 
contagious  matter  as  are  feen  in  fome  variolous  patients,  fo  as 
to  cover  the  whole  fkin  almoft  with  puftules,  does  not  arife 
from  any  chemical  fermentation  in  the  blood,  but  that  it  is  ow- 
ing to  morbid  motions  of  the  fine  extremities  of  the  capillaries 
or  glands,  whether  thefe  be  ruptured  or  not,  appears  from  the 
quantity  of  this  matter  always  correfponding  with  the  quantity 
of  the  fever;  that  is,  with  the  violent  exertions  of  thofe  glands 
and  capillaries  which  are  the  terminations  of  the  arterial  fyftem. 

The  truth  of  this  theory  is  evinced  further  by  a circumftance 
obferved  by  Mr.  J.  Hunter,  in  his  Treatife  on  Venereal  Difeafe ; 
that  in  a patient  who  was  inoculated  for  the  fmall-pox,  and 
who  appeared  afterwards  to  have  been  previoufly  infected  with 
the  meafles,  the  progrefs  of  the  fmall-pox  was  delayed  till  the 
meafles  had  run  their  courfe,  and  that  then  the  fmall-pox  went 
through  its  ufual  periods. 

Two  fimilar  cafes  fell  under  my  care,  which  I fhall  here  re- 
late, as  it  confirms  that  of  Mr.  Hunter,  and  contributes  to  iiluf- 
trate  this  part  of  the  theory  of  contagious  difeafes.  1 have 
tranfcribed  the  particulars  from  a letter  of  Mr.  Lightwood,  of 
Yoxal,  the  furgeon  who  daily  attended  them,  and,  at  my  requeft, 
after  I had  feen  them,  kept  a kind  of  journal  of  their  cafes. 

Mils  H.  and  Mifs  L.  two  lifters,  the  one  about  four  and  the 
other  about  three  years  old,  w?ere  inoculated  Feb.  7, 1791.  On 
the  10th  there  was  a rednefs  on  both  arms  difcernible  by  a glafs. 
On  the  1 ith  their  arms  were  fo  much  inflamed  as  to  leave  no 
doubt  of  the  infection  having  taken  place.  On  the  12th  lefs 
appearance  of  inflammation  on  their  arms.  In  the  evening 

Mifs 


296  DISEASES  OF  SENSATION.  Sect.  XXXIII.  2. 


Mils  L.  had  an  eruption  which  refembled  the  mealies.  On  tire 
13th  the  eruption  on  Mils  L.  was  very  full  on  the  face  and 
breaft,  like  the  mealies,  with  confiderable  fever.  It  was  now 
known,  that  the  mealies  were  in  a farm-houfe  in  the  neighbour,- 
hood.  Mils  H.’s  arm  lefs  inflamed  than  yefterday.  On  the 
14th  Mifs  L.’s  fever  great,  and  the  eruption  universal.  The 
arm  appears  to  be  healed.  Mils  H.*s  arm  fomewnat  redder. 
They  were  now  put  into  feparate  rooms.  On  the  1 h Mifs 
L.’s  arms  as  vefterday,  Eruption  continues.  Mifs  H.  - arms 
have  varied  but  little.  16th,  the  eruptions  on  M*is  L.  : riv- 

ing away;  her  fever  gone,.  Begins  to  have  a little  red  nets  in 
one  arm  at  the  place  of  inoculation.  Mils  H.’s  arms  get  redder, 
but  Hie  has  no  appearance  of  complaint.  20th,  Mifs  L.:s  arms 
have  advanced  flowly  till  this  day,  and  now  a lew  puftules  ap- 
pear. Mifs  H.’s  arm  has  made  little  progrefs  from  the  16th  to 
this  day,  and  now  fhe  has  fome  fever.  21ft,  Mifs  L.  as  vcf- 
terday.  Mil's  H.  has  much  inflammation,  and  an  inereale  of 
the  red  circle  on  one  arm  to  the  hze  of  half  a crown,  and  had 
much  fever  .at  night,  with  fetid  breath.  22d,  Mifs  L.’s  pultules 
continue  advancing.  Mifs  H.’s  inflammation  of  her  arm  and 
red  circle  increafes.  A few  red  fpots  appear  in  different  parts, 
with  fome  degree  of  fever  this  morning.  23d,  Mil's  L.  lias  u 
larger  crop  of  puftules.  Mifs  H.  has  fmall  puftules  and  great 
inflammation  of  her  arms,  with  but  one puftuie  like  to  luppu- 
rate.  After  this  day  they  gradually  got  well,  and  the  puftules 
difappeared. 

In  one  of  Lhefe  cafes  the  mealies  went  through  their  com- 
mon courfe  with  milder  fymptoms  that  ufual,  and  in  the  other, 
the  meally  contagion  leemed  juft  fufficien  : to  ftop  the  proyrefs 
of  variolous  contagion,  but  without  ittelf  throwing  the  con  ki- 
tution  into  any  d border.  At  tire  fame  time  both  the  mealies 
and  fmall-pox  feem  to  have  been  rendered  milder.  Docs  no: 
this  give  an  idea,  that  if  they  were  both  inoculated  at  the  fame 
time,  that  neither  of  them  might  affect  the  patient  r 

From  thefe  cafes  I contend,  that  the  contagious  matter  of 
thefe  difeafes  does  not  affeeft  the  conftitution  by  a fermenta- 
tion, or  chemical  change  of  the  blood,  becaufe  then  thev  muff 
have  proceeded  together,  and  have  produced  a third  fomethir.g, 
not  exactly  ftmilar  to  either  of  them  ; but  that  they  produce  new 
motions  of  the  cutaneous  terminations  of  the  blood  veffeis, 
which,  for  a time,  proceed  daily  with  increafmg  activity,  like 
fome  paroxvfms  of  fever,  till  they  at  length  fecrete  or  form  a 
ftmilar  poifon  by  thefe  unnatural  actions. 

Now,  as  in  the  meafles  one  kind  of  unnatural  motion 
takes  place,  and  in  the  fmall-pex  another  kind,  it  is  ealy  to 

conceive. 


Sect.  XXXIII.  2.  DISEASES  OF  SENSATION.  297 

conceive,  that  thefe  different  kinds  of  morbid  motions  cannot 
exift  together  ; and,  therefore,  that  that  which  has  firft  begun 
will  continue  till  the  fyftem  becomes  habituated  to  the  ftimu- 
his  which  occafiovss  it,  and  has  ceal’ed  to  be- thrown  into  ac- 
tion by  it ; and  then  the  other  kind  of  ftimulus  will,  in  its  turn, 
produce  fever,  and  new  kinds  0!  motions  peculiar  to  itfelf. 

10.  On  further  conftdering  the  adtion  of  contagious  mat- 
ter, ftnee  the  former  part  of  this  work  was  fent  to  the  prefs, 
where  I have  afferted,  in  Se£l.  XII.  3.  6.  that  it  is  probable 
that  the  variolous  matter  is  diffufed  through  the  blood  ; I pre- 
vailed on  my  friend  Mr.  Power,  furgeon  at  Bofworth,  in  Lei- 
cefterfhire,  to  try  whether  the  fmall-pox  could  be  inoculated 
by  ufing  the  blood  of  a variolous  patient,  inftead  of  the  mat- 
ter from  the  puftules  ; as  I thought  fuch  an  experiment  might 
throw  fome  light,  at  leaft,  on  this  intere fling  fubjedl.  The  &1- 
lowing  is  an  extract  from  his  letter  : — 

“ March  11,  1793.  I inoculated  two  children,  who  had 
not  had  the  fmall-pox,  with  blood  which  was  taken  from  a pa- 
tient on  the  lecond  day  after  the  eruption  commenced,  and  be- 
fore it  was  completed.  And  at  the  fame  time  I inoculated  my- 
felf  with  blood  from  the  fame  perl'on,  in  order  to  compare  the 
appearances  which  might  arife  in  a peri’on  liable  to  receive  the 
infedfion,  and  in  one  not  liable  to  receive  it.  On  the  fame 
day  I inoculated  four  other  children,  liable  to  receive  the  in- 
fedfion, with  blood  taken  from  another  perfon  on  the  fourth 
day  after  the  commencement  of  the  eruption.  The  patients 
from  whom  the  blood  was  taken  had  the  diieafs  mildly,  but 
had  the  mod  puftules  or  any  1 could  felecf  from  twenty  in- 
oculated patients ; and  as  much  of  the  blood  was  inftnuated  un- 
der the  cuticle  as  I could  introduce  by  elevating  the  fkiu  without 
drawing  blood ; and  three  or  four  fuch  pundhires  were  made  in 
each  of  their  arms,  and  the  blood  was  ufed  in  its  fluid  jftate. 

“ As  the  appearances  in  all  thefe  patients,  as  well  as  in  my- 
felf,  were  ftmilav,  I ih all  only  mention  them  in  general  terms. 
March  13.  A flight  fubcuticular  difcoloration,  with  rather  a 
livid  appearance,  without  forenefs  or  pain,  was  vilible  in  them 
all,  as  well  as  in  my  own  hand.  15.  The  difcoloration  fome- 
what  lels,  without  pain  or  forenefs.  Some  patients  inoculated 
on  the  fame  day  with  variolous  matter  have  conliderable  in- 
flammation. 17.  The  difcoloration  is  quite  gone  in  them  all, 
and  trom  my  own  hand,  a dry  mark  only  remaining.  And  they 
were  all  inoculated  on  the  1 Sth,  with  variolous  matter,  which 
produced  the  difeafe  in  them  all.” 

Mr.  Power  afterwards  obferves,  that,  as  the  patients  from 
whom  the  blood  was  taken  had  the  diieale  mildly,  it  may  be 

fuppofed., 


29'8  DISEASES  OF  SENSATION.  Sect.  XXXIII.  i. 

fuppofed,  that  though  the  contagious  matter  might  be  mixed 
with  the  blood,  it  might  dill  be  in  too  dilute  a date  to  convey 
the  infection  ; but  adds  at  the  fame  time,  that  he  has  diluted  re- 
cent matter  with  at  lead  five  times  its  quantity  of  water,  and 
which  has  dill  given  the  infedtion ; though  he  has  fometimes 
diluted  it  fo  far  as  to  fail. 

The  following  experiments  were  indituted  at  my  requed  by 
my  friend  Mr.  Hadley,  furgeon  in  Derby,  to  afcertain  whether 
the  blood  of  a perlon  in  the  fmall-pox  be  capable  of  communi- 
cating the  difeafe.  “ Experiment  id.  Odlober  18th,  1793. 
I took  fome  blood  from  a vein  in  the  arm  of  a perfon  who  had 
the  fmall-pox,  on  the  fecondday  of  the  eruption,  and  introduc- 
ed a fmall  quantity  of  it  immediately  with  the  point  of  a lan- 
cet, between  the  lcarf  and  true  fkin  of  the  right  arm  of  a boy 
nine  years  old,  in  two  or  three  different  places  ; the  other  arm 
was  inoculated  with  variolous  matter  at  the  fame  time. 

‘‘  i9th.  The  punctured  parts  of  the  fight  arm  were  furround- 
ed  with  fome  degree  of  fubcuticular  inflammation.  20th.  The 
inflammation  more  confiderable,  vvith  a flight  degree  of  itching, 
but  no  pain  upon  preflure.  2 id.  Upon  examining  the  arm  this 
day  with  a lens,  1 found  the  inflammation  lefs  extenfive,  and  the 
rednefs  changing  to  a deep  yellow  or  orange-colour.  22d.  In- 
flammation nearly  gone.  23d.  Nothing  remained,  except  a flight 
difcoloration  and  a little  fcurfy  appearance  on  the  punctures. 
At  the  fame  time  the  inflammation  of  the  arm  inoculated  with 
variolous  matter  was  increafing  fad,  and  he  had  the  difeafe 
mildly  at  the  ufual  time. 

“ Experiment  2d.  I inoculated  another  child  at  the  fame 
time  and  in  the  fame  manner,  with  blood  taken  on  the  fird  day 
of  the  eruption  ; but  as  the  appearance  and  effedts  were  limilar 
to  thofe  in  the  preceding  experiment,  I fftall  not  relate  them 
minutely. 

“ Experiment  3d.  Odtober  20th.  Blood  w'as  taken  from  a 
perfon  who  had  the  fmall-pox,  on  the  third  day  of  the  erup- 
tion, and  on  the  fixth  from  the  commencement  of  the  erup- 
tive fever.  I introduced  fome  of  it  in  its  fluid  date  into  both 
arms  of  a boy  feven  years  old.  2 id.  There  appeared  to  be 
iome  inflammation  under  the  cuticle,  where  the  pundlures  were 
made.  22d.  Inflammation  more  confiderable.  23d.  On  this 
day  the  inflammation  was  fomewhat  greater,  and  the  cuticle 
rather  elevated.  24th.  Inflammation  much  lefs,  and  only  a 
brown  or  orange  colour  remained.  25th.  Scarcely  anv  de- 
coloration left.  On  this  day  he  was  inoculated  with  variolous 
matter ; the  progrefs  of  the  infedrion  went  on  in  the  ufual  wav, 
and  he  had  the  fmall-pox  very  favourably. 


“ At 


Sj-ct. XXXIII. 2.  DISEASES  OF  SENSATION.  299 

At  this  time  I was  requeued  to  inoculate  a young  perfon, 
who  was  thought  to  have  had  the  fjnall-pox,  but  his  parents 
were  not  quite  certain  ; in  one  arm  I introduced  variolous  mat- 
ter, and  in  the  other  blood,  taken  as  in  experiment  3d.  On 
the  fecond  day  after  the  operation,  the  pundtured  parts  were 
inflamed,  though  I think  the  arm  in  which  I had  inferted  va- 
riolous matter  was  rather  more  fo  than  the  other.  On  the 
third  the  inflammation  was  increafed,  and  looked  much  the  fame 
as  in  the  preceding  experiment.  4th.  The  inflammation  was 
much  diminifhed,  and  on  the  5th  altnoft  gone.  He  was  ex- 
pofed  at  the  fame  time  to  the  natural  infection,  but  has  con- 
tinued perfectly  well. 

“ I have  frequently  obferved  (and  believe  moft  practiti- 
oners have  done  the  fame),  that  if  variolous  matter  be  inferted 
in  the  arm  of  a perfon  who  has  previoufly  had  the  fmall-pox, 
.that  the  inflammation  on  the  fecond  or  third  days  is  much  greater 
than  if  they  had  not  had  the  difeafe,  but  on  the  fourth  or  fifth 
it  difappears. 

“ On  the  23d  I introduced  blood  into  the  arms  of  three 
more  children,  taken  on  the  third  and  fourth  days  of  the  erup- 
tion. The  appearances  were  much  the  fame  as  mentioned  in 
experiments  firft  and  third.  They  were  afterwards  inoculated 
with  variolous  matter,  and  had  the  difeafe  in  the  regular  way. 

“ The  above  experiments  were  made  with  blood  taken  from 
a fmall  vein  in  the  hand  or  foot  of  three  or  four  different  pa- 
tients, whom  I had  at  that  time  under  inoculation.  They  were 
. feledled  from  160,  as  having  the  greateft.  number  of  pul  rules. 
The  part  was  wafned  with  warm  water  before  the  blood  was 
taken,  to  prevent  the  poflibility  of  any  matter  being  mixed  with 
it  from  the  l'urface.” 

Shall  we  conclude  from  hence,  that  the  variolous  matter 
never  enters  the  blood-vefiels  ? but  that  the  morbid  motions  of 
the  vefiels  of  the  fkin  around  the  infertion  of  it  continue  to  in- 
creafe  in  a larger  and  larger  circle  for  fix  or  feven  days ; that 
then  their  quantity  of  morbid  adlion  becomes  great  enough  to 
produce  a fever-fit,  and  to  afFedb  the  ftomach  by  afiociation  of 
motions  ? and  finally,  that  a fecond  afiociation  of  motions  is 
produced  between  the  ftomach  and  the  other  parts  of  the  fkin, 
inducing  them  into  morbid  adlions  fimilar  to  tfiofe  of  the  circle 
round  the  infertion  of  the  variolous  matter  ? Many  more  expe- 
riments and  obfervations  are  required  before  this  important 
queftion  can  be  fatisfaCtorily  anfwered. 

It  may  be  adduced,  that  as  the  matter  inferted  into  the  fkin 
of  the  arm  frequently  fwells  the  lymphatic  in  the  axilla,  that  in 
that  circumftance  it  feems  to  be  there  arrefled  in  its  progrefs, 

R r and 


$o8  DISEASES  OF  SENSATION.  Sect.  XXXIII.  2 

and  cannot  be  imagined  to  enter  the  blood  by  that  lymphatic 
gland  till  the  fwelling  of  it  fubfides.  Some  other  phenomena 
of  the  difeafe  are  more  eafv  reconcileable  to  this  theory  of  lvm- 
pathetic  motions  than  to  that  of  abforption;  as  the  time  taken 
■up  between  the  infertion  of  the  matter,  and  the  operation  of  it 
on  the  fyftem,  as  mentioned  above.  For  the  circle  around  the 
infertion  is  feen  to  increafe,  and  to  inflame;  and  I believe,  un- 
dergoes a kind  of  diurnal  paroxylm  of  torpor  and  palenefs,  with 
a fucceeding  increafe  of  adfion  and  colour,  like  a topical  fever- 
fit.  Whereas,  if  the  matter  is  conceived  to  circulate  tor  fix  or 
feven  days  with  the  blood,  without  produc  ng  dnorder,  it  ought 
to  be  rendered  milder,  or  the  blood-vefTels  more  familiarized  to 
its  acrimony. 

It  is  much  eafier  to  conceive,  from  this  doctrine  of  affociated 
or  fympathetic  motions  of  diftant  parts  > f the  fv hem,  how  it 
happens,  that  the  variolous  infedfion  can  be  received  but  once, 
as  before  explained,  than  by  fuppofing,  that  a change  is  effedt- 
ed  in  the  mals  of  blood  by  any  kind  ot  fermentative  procefs.  , 

The  curious  circumftance  ot  the  two  contagions  ot  fmarl*- 
pox  and  meafles  not  adding  at  the  fame  time,  but  one  of  them 
retting  or  fufpending  its  adtion  till  that  of  the  other  ceafes,  mav 
be  much  eafier  explained  from  fvmpatiietic  or  affociated  actions 
of  the  infedted  part  with  other  parts  of  the  fvftem,  than  it  can 
from  fuppofing  the  two  Contagions  to  enter  the  circulation. 

The  ikin  of  the  face  is  fubjedt  to  more  frequent  viciffitudes 
of  heat  and  cold,  from  its  expcl'ure  to  the  open  air,  and  is  in 
confequence  more  liable  to  fenlitive  affociation  with  the  ftomach 
than  any  other  part  of  die  lurtace  of  the  body,  becaufe  their  ac- 
tions have  been  more  frequently  thus  affociated.  T hus,  in  a 
furfeit  from  drinking  cold  water,  when  a perfon  is  very  hot  and 
fatigued,  an  eruption  is  liable  to  appear  on  the  face  in  conle- 
quence  of  this  fympathy.  In  the  lame  manner  the  roly  erup- 
tion on  the  faces  of  drunkards  more  probably  ariles  from  the* 
fympathy  of  the  face  with  the  ftomach,  rather  than  between  the. 
face  and  die  liver,  as  is  generally  luppofed. 

This  fympathy  between  the  ftomach  and  die  Ikin  of  the  face 
is  apparent  in  the  eruption  of  the  fmall-pox : iince,  where  the 
difeafe  is  in  confiderable  quantity,  the  eruption  on  the  face  firft 
fucceeds  the  ficknefs  of  the  ftomach.  In  the  natural  difeafe  the 
ftomach  leems  to  be  frequently  primarily  affedfed,  either  alone 
or  along  with  the  tonfils,  as  the  matter  feems  to  be  only  ditfuled 
in  the  air,  and  by  being  mixed  with  the  faliva,  or  mucus  of  the 
tonfils,  to  be  fwallowed  into  the  ftomach. 

Atter  l'ome  days  the  irritative  circles  of  motions  become  dif- 
©rdered  by  this  new  ftimulus,  which  adds  upon  the  mucous  lining 

ot 


Sect. XXXIII. 3.  QISEASES  OF  SENSATION.  301 

of  the  ftomach;  and  ficknefs,  vertigo,  and  a diurnal  fever  fuc- 
.ceed.  . Thefe  difordered  irritative  motions  become  daily  increafed 
for  two  or  three  days,  and  then,  by  their  increafed  adlion,  cer- 
tain fenfitive  motions,  or  inflammation,  is  produced;  and  at  the 
next  cold  flt  of  fever,  when  the  ftomach  recovers  from  its  torpor, 
-an  inflammation  of  the  external  Ikin  is,  formed  in  points  (which 
afterv.  ardsfuppurate),  by  fenlitive  aflociation,  in  the  fame  man- 
ner as  a cough  is  produced  in  confequence  of  expoftngthe  feet 
to  cold,  as  defcribed  in  Sed.. XXV.  1.  1.  and .Clafs  IV.  2.  2. 
.4.  If  the  inoculated  fkin  of  the  arm,  as  far  as  it  appears  inflam- 
ed, was  to  be  cut  out,  or  deftroyed  by  cauftic,  before  the  fe- 
ver commenced,  as  fuppofe  on  the  fourth  day  after  inoculation, 
would  this  prevent  the  difeafe  ? as  it  is  fuppofed  to  prevent  the 
hydrophobia. 

II L 1.  Where  the  new  veffels,  and  enlarged  old  ones,  which” 
conftitute  inflammation,  are  not  fohaftily  diuended  as  to  burft, 
and  form  a new  kind  of  gland  for  the  fecretion  of  matter,  as 
above  mentioned;  if  fuc’n  circumftances  happen  as  diminifh  the 
•painful  fenfation,  the  tendency  to  growth  ceafes,  and  by  and  by 
an  abforption  commences,  not  only  of  the  fuperabundant  quan- 
tity of  fluids  depoftted  in  the  inflamed  part,  but  of  the  folids  like- 
wife,  and  this  even  of  the  hardeft  kind. 

Thus,  during  the  growth  of  the  fecond  fet  of  teeth  in  chil- 
dren, the  roots  of  the  ftrft  fee  are  totally  abforbed,  till  at  length 
,nothing  of  them  remains  but  the  crown  ; though  a few  weeks 
before,  if  they  are  drawn  immaturely,  their  roots  are  found  com- 
plete. Similar  to  this  Mr.  Hunter  has  obferved,  that  where  a 
dead  piece  of  bone  is  to  exfoliate,  or  to  feparate  from  a living 
one,  that  the  dead  part  does  not  putrify,  but  remains  perfectly 
found ; while  the  furface  of  the  living  part  of  the  bone,  which  is 
in  contadl  with  the  dead  part,  becomes  abforbed,  and  thus  effedls 
its  feparation.  Med.  Comment.  Edinb.  v.  i.  425.  In  the  fame 
.manner  the  calcareous  matter  of  gouty  concretions,  the  coagu- 
lable  lymph  depoftted  on  inflamed  membranes  in  rheumatifm 
and  extravafated  blood,  become  abforbed  ; which  are  all  as  folid 
.and  as  indifloluble  materials  as  the  new  veflels  produced  in  in- 
flammation. 

This  abforption  of  the  new  veflels  and  depoftted  fluids  of  in- 
flamed parts  is  called  refolution : it  is  produced  by  firft  ufing 
fuch  internal  means  as  decreafe  the  pain  of  the  part,  and,  in 
confequence,  its  new  motions,  as  repeated  bleeding,  cathartics, 
.diluent  potations,  and  warm  bath. 

After  the  veflels  are  thus  emptied,  and  the  abforption  of  the 
new  veffels  and  depoftted  fluids  is  evidently  begun,  it  is  much 
promoted  by  ftimulating  the  part  externally  by  folutions  of  lead 


3o2  DISEASES  OF  SENSATION.  Sect.  XXXIIT.  3. 

or  other  metals,  and  internally  by  the  bark  and  fmall  doles  of 
opium.  Hence,  when  an  ophthalmy  begins  to  become  paler, 
ariy  acrid  eye-water,  as  a folution  of  fix  grains  of  white  vitriol 
in  an  ounce  ot  water,  haflens  the  abforption,  and  clears  :!,e  eve 
in  a very  fhort  time.  But  the  fame  application  ufed  a few  days 
fooner  would  have  increafed  the  inflammation.  Hence,  after 
evacuation,  opium  in  fmall  doles  may  contribute  to  promote  the 
abforption  of  fluids  depofited  on  the  brain,  as  obfervtd  by  n-ir. 
Bromfleld,  in  his  Treadfe  of  Surgery. 

2.  Where  an  ablcefs  is  formed  by  the  rupture  of  thefe  new 
veflels,  the  violence  of  inflammation  ceal'es,  and  a new  gland 
feparates  a material  called  pus : at  the  fame  time  a lefs  degree 
of  inflammation  produces  new  veffels,  called  vulgarlv  proud 
fiefh ; which,  if  no  bandage  confines  its  growth,  nor  anv  other 
circumftance  promotes  abforption  in  the  wound,  would  rife  to 
a great  height  above  the  uiual  fize  ot  the  part. 

Hence  the  art  of  healing  ulcers  confifts  in  producing  a ten } 
dency  to  abforption  in  the  wound,  greater  than  the  depci; tion. 
Thus,  when  an  ill-conditioned  ulcer  feparates  a copious  and 
thin  difeharge,  by  the  ufe  of  any  ftimulus,  as  of  falts  of  lead,  or 
mercury,  or  copper  externally  applied,  the  difeharge  becomes 
diminifhed  in  quantity,  anti  becomes  thicker  as  die  thinner  parts 
are  find  abforbed. 

Bat  nothing  lo  much  contributes  to  increafe  the  abforption 
in  a wound,  as  covering  the  whole  limb  above  the  fore  with  a 
bandage,  which  fhould  be  fpread  with  fome  plaller,  as  with 
emplalbrum  de  minio,  to  prevent  it  from  flipping.  By  this  arti- 
ficial tightnefs  of  the  lkin,  the  arterial  pulfations  act  with  double 
their  ufual  power  in  promoting  the  afeending  current  ot  the 
’fluid  in  the  valvular  lymphatics. 

Internally  the  abf  orption  from  ulcers  fhould  be  promoted  rirft 
by  evacuation,  then  by  opium,  bark,  mercury,  ftcel. 

3.  Where  the  inflammation  proceeds  with  greater  violence 
or  rapidity,  that  is,  when,  by  the  painful  fenfation.  a more  in- 
ordinate activity  of  the  organ  is  produced,  and,  by  this  great 
activity,  an  additional  quantity  ot  painful  fenlarion  follows  in 
an  increafing  ratio,  till  the  whole  of  the  fenforial  power,  or 
fpirit  of  animation,  in  the  part  becomes  exha u fled,  a mortifica- 
tion enfues,  as  in  a carbuncle,  in  inflammations  of  the  bowels, 
jn  the  extremities  of  old  people,  or  in  the  limbs  of  thofe  who 
are  brought  near  a.  fire  after  having  been  much  benumbed  with 
cold.  And  from  hence  it  appears,  why  weak  people  are  more 
fubject  to  mortification  than  ftrong  ones,  and  why,  in  weak 
perfons,  lefs  pain  will  produce  mortification,  namely,  bccaufc 
the  fenforial  power  is  iconer  exha u fled  by  an  excels  ot  aeftivu  > . 


Sect.  XXXIII.  4.  DISEASES  OF  SENSATION.  303 

I remember  feeing  a gentleman  who  had  the  preceding  day  tra- 
velled two  ftages  in  a chaife,  with  what  he  termed  a bearable 
pain  in  his  bowels,  which,  when  I faw  him,  had  ceafed  rather 
luddenly,  and  without  a paffage  through  him:  his  ptilfe  was 
then  weak,  though  not  very  quick  ■ but  as  nothing  which  he 
fwallowed  would  continue  in  his  ftomach  many  minutes,  I 
concluded  that  the  bowel  was  mortified:  he  died  on  the  next 
day.  It  is  ufual  for  patients  finking  under  the  fmall-pox,  with 
mortified  puftules,  and  with  purple  fpots  intermixed,  to  complain 
of  no  pain,  but  to  fay  they  are  pretty  well  to  the  laft  moment. 

Recapitulation. 

IV.  When  the  motions  of  any  part  of  the  fyftem,  in  confe- 
quer.ce  ol  previous  torpor,  are  performed  with  more  energy 
than  in  the  irritative  fevers,  a difagreeable  fenfation  is  produced, 
and  new'  actions  of  fome  part  of  the  fyftem  commence  in  con- 
fequence  of  this  fenfation,  conjointly  with  the  irritation;  which 
motions  conftitute  inflammation.  If  the  fever  be  attended  with 
a ftrong  pulle,  as  in  pleurify  or  rheumatiim,  it  is  termed  fynecha 
fenfitiva,  or  fenfitive  fever  with  ftrong  pulfe;  which  is  ufually 
termed  inflammatory  fever.  If  it  be  attended  with  weak  pulfe, 
it  is  termed  typhus  fenfitivus,  or  feniitive  fever  with  weak 
pulfe  ; or  typhus  gravior,  or  putrid  malignant  fever. 

The  fynocha  fenfitiva,  or  fenfitive  fever  with  ftrong  pulfe, 
is  generally  attended  with  fome  topical  inflammation,  as  in  pe- 
ripneumony,  hepatitis,  and  is  accompanied  with  much  coagu- 
lable  lymph,  or  iize ; which  riles  to  the  furface  of  the  blood, 
when  taken  into  a bal'on,  as  it  cools;  and  which  is  believed  to 
be  the  increafed  mucous  fecretion  from  the  coats  of  the  arteries, 
infpiffated  by  % greater  abforption  of  its  aqueous  and  faline 
part,,  and  perhaps  changed  by  its  delay  in  the  circulation. 

The  typhus  fenfitivus,  or  fenfitive  fever  with  weak  pulfe,  is 
frequently  attended  with  delirium,  which  is  caufed  by  the  defi- 
ciency of  the  quantity  of  fenforial  power,  and  with  variety  of 
cutaneous  eruptions. 

Inflammation  is  caufed  by  the  pains  occafioned  by  excefs  of 
adlion,  and  not  by  thofe  pains  which  are  occafioned  by  defedt 
of  action.  Thefe  morbid  adfions,  which  are  thus  produced 
by  two  fenforial  powers,  viz.  by  irritation  and  fenfation,  fe- 
crcte  new  living  fibres,  which  elongate  the  old  vefiels,  or  form 
new  ones,  and,  at  the  fame  time,  much  heat  is  evolved  from  thefe 
combinations.  By  the  rupture  of  thefe  veflels,  or  by  a new 
confcrudtion  of  their  apertures,  purulent  matters  are  fecreted  of 
various  kinds ; which  are  infedtious  the  firft  time  they  are  ap- 
plied to  the  fkin  beneath  the  cuticle,  cr  fwallowed  with  the  fa- 

liva 


304  DISEASES  OF  SENSATION.  Sect.  XXXIII.  4 

liva  into  the  llomach.  This  contagion  adds  not  by  its  bein" 
abforbed  into  the  circulation,  but  by  the  fympathies,  or  afloci- 
ated  actions,  between  the  part  firft  Simulated  by  the  contagious 
matter  and  the  other  parts  of  the  fyftem.  Thus,  in  the  natural 
fmall-pox  the  contagion  is  fwallowed  with  the  faliva,  and  by 
its  ftimulus  inflames  the  ftomacb : this  variolous  inflammation 
of  the  ftomach  increafes  every  day,  like  the  circle  round  the 
pundfure  of  an  inoculated  arm,  till  it  becomes  great  enough  to 
diforder  the  circles  of  irritative  and  fenfltive  motions,  and  thus 
produces  fever-fits,  with  ficknefs  and  vomiting.  Laftly,  after 
the  cold  paroxvfm,  or  tit  of  torpor,  of  the  ftomach  has  in- 
creafed  for  two  or  three  fucceflive  days,  an  inflammation  of  the 
fkin  commences  in  points;  which  generally -fir  ft  appear  upon 
the  face,  as  the  aflociated  actions  between  the  fkin  ot  the  face 
and  that  of  the  ftomach  have  been  more  frequently  exerted  to- 
gether than  thofe  of  any  other  parts  of  the  external  furface. 

Contagious  matters,  as  thofe  of  the  meafles  and  fmall-pox, 
do  not  add  upon  the  fyftem  at  the  fame  time;  but  the  progrefs 
of  that  which  was  laft  received  is  delayed,  till  the  action  of  the 
dormer  infection  ceafes.  All  kinds  of  matter,  even  that  from 
common  ulcers,  are  probably  contagious  the  firll  time  they  are 
inlerted  beneath  the  cuticle,  or  fwallowed  into  the  ftomach  ; that 
is,  as  they  w'ere  formed  by  certain  morbid  addions  of  the  extre- 
mities of  the  veflels,  they  have  the  power  to  excite  timilar  mor- 
bid actions  in  the  extremities  of  other  veflels,  to  which  they  are 
"applied ; and  thefe  by  fympathy,  or  aflbciations  of  motion,  ex- 
cite fimilar  morbid  addions  in  diftant  parts  of  the  fyftem,  with- 
out entering  die  circulation ; and  hence  the  blood  of  a patient  in 
.the  fmall-pox  will  not  give  that  difeafe  by  inoculation  to  others. 

When  the  new  fibres  or  veflels  become  again  abforbed  into 
the  circulation,  the  inflammation  ceafes  ; which  is  promoted 
after  fufficient  evacuations,  by  external  ftimulants  and  banda- 
ges; but  where  the  addion  of  the  veflels  is  very  great,  a morti- 
fication of  the  part  is  liable  to  enfue,  owing  to  the  exhauftion 
of  fenforial  power;  which,  however,  occurs  in  weak  people 
without  much  pain,  and  without  very  violent  previous  inflam- 
mation; and,  like  partial  paralyfis,  may  be  efteeined  one  mode 
of  natural  death  of  old  people,  a part  d\*ng  before  the  whole. 


SECT. 


Sect.  XXXIV.  r.  DISEASES  OF  VOLITION'.  335- 


SECT.  XXXIV. 

DISEASES  OF  VOLITION-. 

L I.-  Volition  defined.  Motions  termed  involuntary  are- 
caufied  by  volition.  Defires  oppofed  to  each  other.  Deli- 
beration. Afis  between  two  hay-cocks.  Saliva  ['wallowed 
againfl  one' s de/ire.  V oluntary  motions  difiinguijhed  from 
thofie  afj'ociated  with  fenfitive  motions.  2.  Pains  from  ex- 
cefis,  and  from  defedt  of  motion..  No  pain  is  felt  during 
vehement  voluntary  exertion ; as  in  cold  fits  of  ague , la- 
bour-pains, Jlranguary,  tenefmus,  vomiting,  refllefnefs  in 
fevers,  convulfion  of  a wounded  mufcle.  3.  Of  holding 
the  breath  and  fereaming  in  pain  : why  [wine  and  dogs 
cry  out  in  pain,  and  not  Jhecp  and  horfes.  Of  grinning 
and  biting  in  pain:  why  mad  animals  bite  ethers.  4. 
Epileptic  convulfions  explained : why  the  fits  begin  with 
quivering  of  the  under  jaw,  biting  the  tongue,  and  felting 
the  teeth  : why  the  convuljive  motions  are  alternately  re- 
laxed. The  phenomenon  of  laughter  explained.  Why 
children  cannot  tickle  themj elves.  How  [ome  have  died 

from  immoderate  laughter.  5.  Of  cataleptic  fpafms,  cf 
the  locked  jaw,  of  painful  cramps.  6.  Syncope  explained. 
Why  no  external  objects  are  perceived  in  fyncopc.  7.  Of 
palfy  and  apoplexy  from  violent  exertions.  Cafe  of  Mrs. 
Scot.  From  dancing,  [eating,  fwimming.  Cafe  of  Mr. 
Nairn.  Why  palfies  are  not  always  immediately  preceded 
by  violent  exertions.  Palfy  and  epilcpfy  from  difeafed 
livers.  Why  the  right  arm  more  frequently  paralytic  than 
the  left.  How  paralytic  limbs  regain  their  motions.  II. 
Difeafes  of  the  fenfual  motions  from  cxcefs  or  defeCt  of 
voluntary  exertion.  I.  Madncfs.  2.  Diflinguifhed from 
delirium.  3.  Why  mankind  more  liable  to  infanity  than 
brutes.  4.  Sufpicion.  Want  of  Jhame  and  of  cleanlinefs. 
5.  They  bear  cold,  hunger  and  fatigue.  Charles  XII.  of 
Sweden.  6.  Pleafureable  delirium,  and  infanity.  Child 
riding  on  a flick.  Pains  of  martyrdom  not felt.  q.Dropfy. 
8.  Inflammation  cured  by  infanity.  III.  1.  Pain  relieved 
by  reverie.  Reverie  is  cm  exertion  of  voluntary  and  fen- 
Jitive  motions.  2.  Cafe  of  reverie.  3.  Lady  fuppofed  to 
have  two  fouls.  4.  Methods  of  relieving  pain. 

I.  1.  BEFORE  we  commence  this  Sedition  on  Difeafed 

Voluntary  Motions,  it  may  be  neceflfary  to  premife,  that  the 

word  volition  is  not  ufed  in  this  work  exactly  in  its  common 

acceptation. 


306  DISEASES  OF  VOLITION.  Sect.  XXXIV.?. 

acceptation.  Volition  is  laid,  in  Se&ion  V.  to  bear  the  fame 
analogy  to  defire  and  averfion,  which  fenfation  does  to  pleafure 
and  pain.  And  hence,  that  when  defire  or  averfion  produces 
any  adhon  of  the  mufcular  fibres,  or  of  the  organs  of  fenfe, 
they  are  termed  volition;  and  the  actions  produced  in  confe- 
quence are  termed  voluntary  actions.  Whence  it  appears,  that 
motions  of  our  muicles  or  ideas  mav  be  produced  in  coniequence 
of  defire  or  averfion,  without  our  having  the  power  to  prevent 
them;  and  yet  thefe  motions  may  be  termed  voluntary,  accord- 
ing to  our  definition  of  the  word;  though,  in  common  lan- 
guage, they  would  be  called  involuntary. 

The  objedhs  of  defire  and  averfion  are  generally  at  a diftance, 
whereas  thofe  of  pleafure  and  pain  are  immediately  afting  upon 
our  organs.  Hence,  before  defire  or  averfion  is  exerted,  fo 
as  to  caufe  any  adtions,  there  is  generally  time  for  deliberation  ; 
which  confifts  in  difeovering  the  means  to  obtain  the  objedl  of 
defire,  or  to  avoid  the  objedf  of  averfion,  or  in  examining  the 
good  or  bad  consequences  which  may  refult  from  them.  In 
this  cafe  it  is  evident  that  we  have  a power  to  delay  the  pro- 
poied  adtion.  or  to  perform  it;  and  this  power  of  chooiing, 
whether  we  fha.ll  ad?c  or  not,  is,  in  common  language,  expreffed 
by  the  word  volition,  or  will.  Whereas,  in  this  work  the 
werd  volition  means  fimply  the  adlive  ftate  of  the  le.ilorial  fa- 
culty in  producing  motion  in  coniequence  of  defire  or  averfion, 
whether  we  have  the  power  of  reitraining  that  adlion  or  not; 
that  is,  whether  we  exert  any  adfions  in  confequence  of  oppo- 
Tite  defires  or  averfions,  or  not. 

For  if  the  objects  of  defire  or  averfion  are  prefent,  there  is 
no  neceffity  to  inveftigate  or  compare  die  means  of  obtaining 
them,  nor  do  we  always  deliberate  about  their  ccnfequences  ; 
that  is,  no  deliberation  neceffarily  intervenes,  and,  in  conie- 
quence, the  power  of  choofing  to  adt  or  not  is  not  exerted.  It 
is  probable,  that  this  two-fold  ufe  of  the  word  volition  in  ail 
languages,  has  confounded  the  metaphvficians,  who  have  de- 
puted about  free  will  and  neceffity.  W hereas,  from  the  above 
analyfis,  it  would  appear,  that  during  our  deep  we  ufe  no  vo- 
luntary exertions  at  all ; and  in  our  waking  hours,  that  thev  are 
the  confequence  ol  defire  or  averfion. 

To  will,  is  to  act  in  confequence  of  defire;  hot  to  defire, 
means  to  defire  fomething,  even  if  that  fomething  be  only  to 
become  free  from  the  pain  which  cauies  the  delire ; for  to  defire 
nothing,  is  not  to  defire:  the  word  defire,  therefore,  includes 
both  the  adlion  and  the  object  or  motive;  for  the  object  and 
motive  of  detire  are  the  fame  thing.  Hence,  to  defire  without 
an  object,  that  is,  widiout  a motive,  is  a fOicC  ifui  in  language. 


Sect. XXXIV.  i.  DISEASES  OF  VOLITION.  307 

As  if  one  fhould  alk,  if  you  could  eat  without  food,  or  breathe 
without  air. 

From  this  account  of  volition  it  appears,  that  convullions  of 
the  mufoles,  as  in  epileptic  tits,  may,  in  the  common  fenfe»of 
that  word,  be  termed  involuntary ; becaufe  no  deliberation  is  in- 
terpofed  between  the  delire  or  averfion  and  the  confequent  ac- 
tion ; but  in  the  fenfe  of  the  word,  as  above  defined,  they  belong 
to  the  clafs  of  voluntary  motions,  as  delivered  in  Vol.  ii.  Clafs 
III.  If  this  ufe  of  the  word  be  difcordant  to  the  ear  of  the  rea- 
der, the  term  morbid  voluntary  motions,  or  motions  in  confe- 
quence  of  averfion,  may  be  fubflituted  in  its  Head. 

Il  a perfon  has  a delire  to  be  cured  of  the  ague*,  and  has  at  the 
fame  time  an  averfion  (or  contrary  defire)  to  fwallowing  an 
ounce  of  Peruvian  bark,  he  balances  defire  again!!  delire,  or 
averfion  again!!  averfion ; and  thus  he  acquires  the  power  of 
choofing,  which  is  the  common  acceptation  of  the  word  wil- 
ling. But  in  the  cold  lit  of  ague,  after  having  difcovered  that 
the  ad!  of  lhuddering,  or  exerting  the  fubcutaneous  mufcles,  re- 
lieves the  pain  of  cold,  he  immediately  exerts  this  a<£!  o voli- 
tion, and  fhudders,  as  foon  as  the  pain  and  confequent  averfion 
return,  without  any  deliberation  intervening:  yet  is  this  ad!, 
as  well  as  that  of  fwallowing  an  ounce  of  the  bark,  caufed  by 
volition ; and  that  even  though  he  endeavours  in  vain  to  prevent 
it  by  a weaker  contrary  volition.  Tills  recalls  to  our  minds 
the  flory  of  the  hungry  afs  between  two  hay-ftacks,  where  the 
two  defires  are  fuppofed  fo  exadlly  to  countered!  each  other, 
that  he  goes  to  neither  of  the  Hacks,  but  perifhes  by  want. 
Now,  as  two  equal  and  oppofite  defires  are  thus  fuppofed  to 
balance  each  other,  and  prevent  all  adlion,  it  follows,  that  if 
one  of  thefe  hay-i!acks  was  fuddenly  removed,  that  the  afs  would 
irrefiftibly  be  hurried  to  the  other,  which,  in  the  common  ufe  of 
the  word,  might  be  called  an  involuntary  ad!;  but  which,  in 
our  acceptation  of  it,  would  be  clalfed  among!!  voluntary  ac- 
tions, as  above  explained. 

. Hence,  to  deliberate  is  to  compare  oppofing  defires  or  aver- 
llons,  and  that  which  is  the  moft  intereftmg  at  length  prevails, 
and  produces  adlion.  Similar  to  this,  where  two  pains  oppofe 
each  other,  the  ftronger  or  more  interelfing  one  produces  ac- 
tion ; as  in  pleurify  the  pain  from  fuffocation  would  produce 
Cxpanllon  ol  the  lungs,  but  the  pain  occafioned  by  extending 
the  inflamed  membrane,  which  lines  the  chef!,  oppofes  this  ex- 
panfion,  and  one  or  the  other  alternately  prevails. 

When  any  one  moves  his  hand  quickly  near  another  perfon’s 
eyes,  the  eye-lids  inftantly  clofe : this  ad!,  in  common  language, 
is  termed  involuntary,  as  we  have  not  time  to  deliberate  or  to 

S s exert 


SoS  DISEASES  OF  VOLITION'.  Sect.  XXXIV.  r. 

exert  any  contrary  defire  or  averfion;  but  in  this  work  it  would 
be  termed  a voluntary  adb,  becaufe  it  is  caufed  by  the  faculty 
of  volition,  and  after  a few  trials  the  nedbitation  can  be  pre- 
vented by  a contrary  or  oppoftng  volition. 

The  power  of  oppoftng  volitions  is  bell  exemplified  in  the 
ftory  of  Mutius  Sctevola,  who  is  faid  to  have  thruft  his  hand 
into  the  fire  before  Porcenna,  and  to  have  f offered  it  to  be  con- 
fumed  for  having  tailed  him  in  his  attempt  on  the  life  of  that  ge- 
neral. Here  the  averfion  for  the  lofs  of  fame,  or  the  unfatisfi- 
ed  deli  re  to  ferve  his  country,  the  two  prevalent  enthufiafms  at 
that  time,  were  more  powerful  than  the  defire  of  withdrawing 
his  hand,  which  muft  be  occalioned  by  the  pain  of  combuftion  ; 
of  thefe  oppofing  volitions 

Vincet  amor  patriae,  laudumque  immensa  cupido. 

If  any  one  is  told  not  to  fwallow  his  faliva  for  a minute,  he 
foon  fwallows  it  contrary  to  his  will,  in  the  common  fenfe  of 
that  word ; but  this  alfo  is  a voluntary  adbion,  as  it  is  perforn*- 
eJ  by  the  faculty  of  volition,  and  is  thus  to  be  underftood. 
When  the  power  ot  volition  is  exerted  on  any  of  our  fenfes, 
they  become  more  acute,  as  in  our  attempts  to  hear  fmall  noifes 
in  the  night;  as  explained  in  Sedbion  XIX.  6,  Hence,  by 
our  attention  to  the  fauces,  from  our  defire  not  to  fwallow  our 
faliva,  the  lances  becomes  more  feniible  ; and  the  ftimulus  of 
the  faliva  is  followed  by  greater  fenfation,  and  confequent  de- 
fire of  fwallow ing  it.  So  that  the  defire  or  volkion,  in  confe- 
quence  of  the  increafed  fenfation  cf  the  faliva,  is  more  power- 
ful than  the  previous  defire  not  to  fwallow  it.  See  vol.  ii. 
Deglutitio  invua.  In  the  fame  manner,  if  a model!  man  withes 
not  to  want  to  make  water,  when  he  is  confined  with  ladies  in 
a coach  or  an  affembly-room,  that  very  act  of  volition  in- 
duces the  circumlbance  which  he  wilhes  to  avoid,  as  above 
explained  ; infomuch,  that  I once  faw  a partial  infanitv,  which 
might  be  called  a voluntary  diabetes,  which  was  occalioned  by 
the  rear  (and  confequent  averfion)  of  not  being  able  to  make 
water  at  all. 

Ic  is  fur  ther  necelfary  to  obferve  here,  to  prevent  anv  con- 
fftfion  ol  voluntary  with  fenfitive,  or  aflbeiate  motions,  that 
in  all  the  inltances  of  violent  efforts  to  relieve  pain,  thefe  ef- 
forts are  at  firft  voluntary  exertions  ; but  after  they  have  been 
frequently  repeated  for  the  purpofe  of  relieving  certain  pains, 
they  become  alfociated  with  thofe  pains,  and  ceafe,  at  thole 
times,  to  be  fublervient  to  the  will;  as  in  coughing,  fneezing, 
and  ftrangury.  Of  thefe  motions  thofe  which  contribute  to 
remove  or  difiodge  the  offending  caule,  as  the  actions  of  th« 

‘t  abdominal 


Sect.  XXXIV.  i.  DISEASES  OF  VOLITION.  309 

, abdominal  mufcles  in  parturition,  or  in  vomiting,  though  they 
were  originally  excited  by  volition,  are  in  this  work  termed  fen- 
(ihive  motions ; but  thofe  adtions  of  the  mufcles  or  organs  of 
;fenfe,  which  do  not  contribute  to  remove  the  offending  caufe, 
as  in  general  convuifions  or  in  madnefs,  are  in  this  work  term- 
ed voluntary  motions,  or  motions  in  confequence  of  averfion, 
though,  in  common  language,  they  are  called  involuntary  ones. 
Thofe  fenfftive  uiyeftrainable  adtions  which  contribute  to  re- 
move thecaufe  of  pain,  are  uniformly  and  invariably  exerted, 
as  in  coughing  or  fneezing;  but  thofe  motions  which  are  ex- 
eited  in  confequence  of  avrrnon  without  contributing  to  re- 
move  the  painful  caufe,  but  only  to  prevent  the  fenfation  of  it, 
as  in  epileptic  or  cataleptic  fits,  are  not  uniformly  and  invari- 
ably exerted,  but  change  from  onefet  of  mufcles  to  another,  as 
will  be  further  explained;  and  may,  by  this  -criterion  alfo,  be 
diPcinguifhed  from  the  former. 

At  the  fame  time  thofe  motions  which  are  excited  by  per- 
petual ftimulus,  or  by  aflociation  with  each  other,  or  imme- 
diately by  pleafureable  or  painfyl  fenfation,  may  properly  be 
termed  involuntary  motions,  as  thofe  of  the  heart  and  arteries; 
as  the  faculty  of  volition  feldom  affedts  thofe,  except  when  it 
exifts  in  unnatural  quantity,  as  in  maniacal  people. 

2.  It  was  obferved  in  Section  XIV.  on  the  Production  of 
Ideas,  that  thofe  parts  of  the  fyftem  which  are  ufuallv  termed 
the  organs  of  fenfe,  are  liable  to  be  excited  into  pain  by  the  ex- 
cefs of  the  ftimulus  of  thofe  objects  which  are,  by  nature, 
adapted  to  affedt  them ; as  of  too  great  light,  found,  or  pref- 
fure.  But  that  thefe  organs  receive, no  pain  from  the  defedt  or 
abfence  of  thefe  ftimuli,  as  in  darknefs  or  filence.  But  that 
our  other  organs  of  perception,  which  have  generally  been 
.called  appetites,  as  of  hunger,  third,  want  of  heat,  want  of 
frefh  air,  are  liable  to  be  affedted  with  pain  by  the  defect,  as 
well  as  by  the  excefs  of  their  appropriated  ftimuli. 

This  excefs  or  defedt  of  ftimulus  is,  however,  to  beconftuer- 
ed  only  as  the  remote  caufe  of  the  pain,  the  immediate  caufe 
being  the  excefs  or  defedt  of  the  natural  adtion  of  the  affedted 
part,  according  to  Sedt.  IV.  5.  Hence  all  the  pains  of  the  body 
may  be  divided  into  thofe  from  excefs  of  motion,  and  thofe  from 
defedt  of  motion  ; which  diftindtion  is  of  great  importance  in 
the  knowledge  and  cure  of  many  difeafes.  For  as  the  pains 
from  excefs  of  motion  either  gradually  fubfide,  or  are  in  gene- 
ral fucceeded  by  inflammation;  fo  thofe  from  defedt  of  motion 
either  gradually  fubfide,  or  are  in  general  fucceeded  by  convul- 
sion or  madneis.  Thefe  pains  are  eaftly  diftinguiihable  from 
each  other  by  this  circumftance,  that  the  former  are  attended 

with 


310  DISEASES  OF  VOLITION.  Sect.  XXXIV.  i 

with  heat  of  the  pained  part,  or  of  the  whole  body ; whereas 
the  latter  exifts  without  increafe  of  heat  in  the  pained  part,  and 
is  generally  attended  with,  coldnefs  of  the  extremities  of  the  bo- 
dy ; which  is  the  true  criterion  of  what  have  been  called  nci  - 
vous  pains. 

Thus,  when  any  acrid  material,  as  fnuff  or  lime,  falls  into 
the  eye,  pain,  and  inflammation,  and  heat,  are  produced  from  tiie 
excels  of  ftimulus ; but  violent  hunger,  hemicrania,  or  the  cla- 
vus  hyftericus,  are  attended  with  coldnefs  of  the  extremities, 
and  defect  of  circulation.  When  we  are  expofed  to  great 
cold,  the  pain  we  experience  from  die  deficiency  of  heat  is  at- 
tended with  a quiefcence  of  the  motions  of  the  valcular  fyftem  ; 
fo  that  no  inflammation  is  produced,  but  a great  defire  of  heat, 
and  a tremulous  motion  of  the  fubcutaneous  mufcles,  which  is 
properly  a convullion  in  confequence  of  this  pain  from  defect 
of  the  ftimulus  of  heat. 

It  was  before  mentioned,  that  as  fenfation  confifts  in  certain 
movements  of  the  fenforium,  beginning  at  fome  of  the  extremi- 
ties of  it,  and  propagated  to  the  central  parts  of  it;  lo  volition 
confifts  of  certain  other  movements  of  the  fenforium,  com- 
mencing in  the  central  parts  of  it,  and  propagated  to  fome  of  its 
extremities.  This  idea  of  thefe  two  great  powers  of  motion  in  , 
the  animal  machine  is  confirmed  from  obferving,  that  they  ne- 
ver exift  in  a great  degree  or  univerfally  at  the  fame  time ; for 
while  we  ftrongly  exert  our  voluntary  motions,  we  ceafe  to  feel 
the  pains  or  uneaftnefles  which  occalioned  us  to  exert  them. 

Hence,  during  the  time  of  fighting  with  lifts  or  fwords  no  pain 
is  felt  by  the  conbatants,  till  they  ceafe  to  exert  themfelves. 
Thus,  in  the  beginning  of  ague-tits,  the  painful  fenfation  of  cold 
is  diminilhed,  while  the  patient  exerts  htmfelf  in  the  I hivering 
and  gnafliing  of  his  teeth.  He  then  ceafes  to  exert  himfelf,  and 
the  pain  of  cold  returns;  and  he  is  thus  peipetually  induced  to 
reiterate  thefe  exertions,  from  which  he  experiences  a tempo- 
rary relict.  The  fame  occurs  in  labour-pains ; the  exertion  of 
the  parturient  woman  relieves  the  violence  of  the  pains  for  a 
time,  which  recur  again  foon  after  fhe  has  ceafed  to  ufe  thofe 
exertions.  The  fame  is  true  in  many  other  painful  difeafes,  as 
in  the  ftrangurv,  tenefmus,  and  the  efforts  of  vomiting;  all  thefe 
dilagreeabie  ienfations  are  diminifhed  or  removed  for  a time  by 
the  various  exertions  they  occasion,  and  recur  alternately  with 
thole  exertions. 

The  reftlefiiiefs  in  fome  fevers  is  an  almoft  perpetual  exer- 
tion of  this  kind,  excited  to  relieve  fome  dilagreeabie  i'enia- 
tions;  the  reciprocal  oppofite  exertions  of  a wounded  worm, 
the  alternate  emprofthotonos  and  opifthotonos  of  fome  ipafmoutc 

difeafes. 


Sect.  XXXIV.  i.  DISEASES  OF  VOLITION.  31  r 

difeafes,  and  the  intervals  of  all  convulfions,  from  whatever 
caufe,  l'eem  to  be  owing  to  this  circumftance  of  the  laws  of  ani- 
mation ; thav  teat  or  univerfal  exertion  cannot  exift  at  the  fame 
time  with  great  or  univerfal  fenfation,  though  they  can  exift 
reciprocally ; which  is  probably  refolvable  into  the  more  general 
law,  that  the  whole  fenforial  power  being  expanded  in  one  mode 
of  exertion,  there  is  none  to  (pare  for  any  other.  Whence  fyn- 
cope,  or  temporary  apoplexy,  fucceeds  to  epileptic  convulfions. 

3.  Hence,  when  any  violent  pain  alRidls  us,  of  which  we 
can  neither  avoid  nor  remove  the  caufe,  we  foon  learn  to  en- 
deavour to  alleviate  it,  by  exerting  fome  violent  voluntary  effort, 
as  mentioned  above and  are  naturally  induced  to  ufe  thofe 
mufcles  for  this  purpofe,  which  have  been,  in  the  early  periods 
or  our  lives,  molt  frequently  or  mod  powerfully  exerted. 

Now,  the  firft  mufcles  which  infants  ufe  moft  frequently, 
are  thofe  of  refpiration;  and,  on  this  account,  we  gain  a habit 
of  holding  our  breath,  at  the  fame  time  that  we  ufe  great  efforts 
to  exclude  it,  for  the  purpofe  of  alleviating  unavoidable  pain ; 
or  we  prefs  out  our  breath  through  a fmall  aperture  of  the  la- 
rynx, and  fcream  violently,  when  the  pain  is  greater  than  is 
relievable  by  the  former  mode  of  exertion.  Thus  children 
fcream  to  relieve  any  pain  either  of  body  or  mind,  as  from  an- 
ger, or  fear  of  being  beaten. 

• Hence  it  is  curious  to  obferve,  that  thofe  animals  who  Ijave 
more  frequently  exerted  their  mufcles  of  refpiration  violently, 
as  in  talking,  barking,  or  grunting,  as  children,  dogs,  hogs, 
fcream  much  more,  when  they  are  in  pain,  than  thofe  other 
animals  who  ufe  little  or  no  language  in  their  common  modes 
of  life,  as  horfes,  lheep,  and  cows. 

The  next  moft  frequent  or  moft  powerful  efforts  which  in- 
fants are  firft  tempted  to  produce,  are  thofe  with  the  mufcles  in 
biting  hard  fubftances:  indeed,  the  exertion  of  thefe  mufcles  is 
very  powerful  in  common  maftication,  as  appears  from  the  pain 
we  receive,  if  a b.it  of  bone  is  unexpectedly  found  amongft  our 
fofter  food ; and  further  appears  from  their  acting  to  fo  great 
mechanical  dilad vantage,  particularly  when  we  bite  with  the 
incifores,  or  canine  teeth;  which  are  firft  formed,  and  thence 
are  firft  ufed  to  violent  exertion. 

Hence,  when  a perfon  is  in  great  pain,  the  caufe  of  which 
he  cannot  remove,  he  fets  his  teeth  firmly  together,  or  bites 
fome  fubftance  between  them  with  great  vehemence,  as  another 
mode  of  violent  exertion  to  produce  a temporary  relief.  Thus 
we  have  a proverb,  where  no  help  can  be  had  in  pain,  “ to 
grin  and  abide and  the  tortures  of  hell  are  faid  to  be  attended 
with  “ gnafhing  of  teeth.” 


Hence, 


312 


DISEASES  OF  VOLITION.  Sect.  XXXIV.  i. 


Hence,  in  violent  fpafmodic  pains,  I have  feen  people  bite 
mot  only  their  tongues,  but  their  arms  or  fingers,  or  thole  of  the 
attendants,  or  any  object  which  was  near  them ; and  alfo  PcrLe, 
pinch,  or  tear  others  or  themfelves,  particularly  the  part -of  their 
own  body  which  is  painful  at  the  time.  Soldiers  who  die  of 
painful  wounds  in  battle,  are  faid  by  Homer  to  bite  the  ground. 
Thus,  alfo,  in  the  belion,  crcoiica  faturnina,  the  patients  are 
faid  to  bite  their  own  flefh,  and  dogs  in  this  difeale  to  bite  up 
the  ground  they  lie  upon.  It  is  probable  that  the  great  end  sa- 
vours to  bite  in  mad  dogs,  and  the  violence  of  other  mad  ani- 
mals, is  owing  to  the  fame.caufe. 

4.  If  the  efforts  of  our  voluntary  motions  are  exerted  a ith 
ftill  greater  energy  for  the  relief  of  fome  difagreeable  fenfation, 
convulfions  are  pioduced;  as  the  various  kinds  of  epilepfy,  and 
in  fome  hyfteric  paroxyfms.  In  all  thefe  diieafes  a pain  or  dif- 
agreeable fenfation  is  produced,  frequently  by  worms,  or  acidity 
in  the  bowels,  or  by  a difeafed  nerve  in  the  fide  or  head,  or  by 
the  pain  cf  a difeafed  liver. 

In  fome  conductions  a more  intolerable  degree  of  pain  is 
produced,  in  fome  part,  at  a di fiance  from  the  caufe,  bv  lenfitive 
afiociation,  as  before  explained:  thefe  pains,  in  fuch  conftitu- 
tions,  arife  to  fo  great  a degree,  that  I verily  believe  no  artificial 
tortures  could  equal  fome  which  I have  witneffed ; and  am 
confident  life  would  not  have  iong  been  preferred,  unlefs  they 
had  been  foon  diminifhed  or  removed  by  the  univerfal  convul- 
fion  of  the  voluntary  motions,  or  by  temporary  madnefs. 

In  fome  of  the  unfortunate  patients  I have  obferved,  the  pain 
has  rifen  to  an  inexpreffible  degree,  as  above  deferibed,  before 
the  convulfions  have  iupei  veiled,  and  which  were  preceded  by 
fereaming  and  grinning:  in  others,  as  in  the  common  epilepfy, 
the  convulfion  lias  immediately  lucceeded  the  commencement 
of  the  difagreeable  fenfations;  and  as  a ftupor  frequently  fuc- 
ceeds  the  convulfions,  'they  only  feemed  to  remember  that  a pain 
at  the  ftomach  preceded  the  fit,  or  fome  other  uneafy  feel ; or 
more  frequently  retained  no  memory  at  all  of  the  immediate 
caufeof  die  paroxyfm.  But  even  in  this  kind  of  epilepfy,  where 
the  patient  does  not  recoiled!  any  preceding  pain,  the  paroxyfms 
generally  are  preceded  by  a quivering  motion  of  the  under  jaw, 
with  a biting  of  the  tongue : the  teeth  afterwards  become  nrefied 
together  with  vehemence,  and  the  eyes  are  then  convulied,  be- 
fore the  commencement  of  the  univerfal  convulfion,  which  are 
all  efforts  to  relieve  pain. 

The  reafon  why  thefe  convulfive  motions  are  alternately  ex- 
erted and  remitted  was  mentioned  above,  and  in  Sedt.  XII.  1.3. 
'when  the  exertions  are  fuch  as  give  a temporary  relief  to  pain, 

which 


Sect.  XXXIV.  i.  DISEASES  OF  VOLITION.  313 

which  excites  them,  they  ceafe  for  a time,  till  the  pain  is  again 
perceived;  and  then  new  exertions  are  produced  for  its  relief. 
We  fee  daily  examples  of  this  in  the  loud  reiterated  laughter  of 
fome  people : tire  pleafureable  fenfation  which-  excites  this 
laughter  arifes,  for  a time,  fo  high  as  to  change  its  name  and 
become  painful:  the  convulfive  motions  of  the  refpiratory  muf- 
cles  relieve  the  pain  for  a time : we  are,  however,  unwilling  to 
lofe  the  pleafure,  and  prefently  put  a ftop  to  this  exertion,  and 
immediately  the  pleafure  recurs,  and  again  as  inftantly  rifes  into 
pain.  All  of  us  have  felt  the  pain  of  immoderate  laughter ; 
children  have  been  tickled  into  convullions  of  the  whole  body, 
and  others  have  died  in  the  adt  of  laughing,  probably  from  a 
paralyfis  fuceeeding  the  long-continued  actions  of  the  mufcles 
of  refpiration. 

Hence  we  learn  the  reafon  why  children,  who  are  fo  eafily 
excited  to  laugh  by  the  tickling  of  other  people’s  fingers,  can- 
not tickle  themfelves  into  laughter.  The  exertion  of  then- 
hands  in  the  endeavour  to  tickle  themfelves  prevents  the  necef- 
fity  of  any  exertion  of  the  refpiratory  mufcles  to  relieve  the 
excefs  of  pleafureable  affedtion.  See  Sedh  XVII.  3.  5. 

Chryfippus  is  recorded  to  have  died  laughing,  when  an  afs 
was  invited  to  fup  with  him.  The  fame  is  related  of  one  of  the 
popes,  who,  when  he  was  ill,  faw  a tame  monkey  at  his  bedfide 
put  on  the  holy  thiara.  Hall.  Phyf.  T.  iii.  p.  306. 

There  are  inftances  of  epilepfy  being  produced  by  laughing, 
recorded  by  Van  Swieton-,  T.  iii.  402  and, 308.  And  it  is  well 
known,  that  many  people  have  died  inftantaneoufly  from  the 
painful  excefs  of  joy,  which  probably  might  have  been  pre*- 
vented  by  the  exertions  of  laughter. 

Every  combination  of  ideas  which  we  attend  to,  occafions 
pain  or  pleafure:  thofe  which  occafion  pleafure,  furnifh  either 
locial  or  felfifh  pleafure — -either  malicious  or  friendly,  or  Ia- 
feivious,  or  fublime  pleafure ; that  is,  they  give  us  pleafure, 
mixed  with  other  emotions,  or  they  give  us  unmixed  pleafure, 
without  occafioning  any  ether  emotions  or  exertions  at  the 
lame  time.  This  unmixed  pleafure,  if  it  be  great,  becomes 
painful,  like  all  other  animal  motions,  from  ftimuli  of  every 
kind;  and  if  no  other  exertions  are  occaiioned  at  the  fame 
time,  we  ufe  the  exertion  of  laughter  to  relieve  this  pain. 
Hence  laughter  is  occaiioned  by  fuch  wit  as  excites  fimple 
pleafure  v/ithout  any  other  emotion,  fuch  as  pity,  love,  reve- 
rence: for  fublime  ideas  are  mixed  with  admiration,  beautiful 
ones  with  love,  new  ones  with  furprife ; and  thefe  exertions  of 
our  ideas  prevent  the  afilion  of  laughter  from  being  necefTary 
to  relieve  the  painful  pleafure  above  deferibed.  Whence  laugh  - 
able 


314  DISEASES  OF  VOLITION,  Sect.  XXXIV.  r. 

able  wit  confifts  of  frivolous  ideas,  without  connexions  of  anv 
confequence,  fuch  as  puns  on  words,  or  on  phrafes,  incon- 
gruous junXions  of  ideas;  on  which  account  laughter  is  fo 
frequent  in  children. 

Unmixed  pleafure  lefs  than  that  which  caufes  laughter,  caufes 
fleep,  as  in  ringing  children  to  fleep,  or  in  flight  intoxication 
from  wine  or  food.  See  SeX.  XVIII.  12. 

If  the  pains,  or  difagreeable  fenfations  above  deferibed,  do 
not  obtain  a temporary  relief  from  thefe  convulfive  exertions 
of  the  mufcles,  thofe  convulfive  exertions  continue  without 
remiflfon,  and  one  kind  of  catalepfy  is  produced.  Thus,  when 
a nerve  or  tendon  produces  great  pain  by  its  being  inflamed  or 
wounded,  the  patient  fets  his  teeth  firmly  together,  and  grins 
violently,  to  diminifh  the  pain ; and  if  the  pain  is  not  relieved 
by  this  exertion,  no  relaxation  of  the  maxillary  mufcles  takes^ 
place,  as  in  the  convulfions  above  deferibed,  but  the  jaws  re-  f 
main  firmly  fixed  together.  This  locked  jaw  is  the  mod  fre-B 
quent  inftance  of  cataleptic  fpafm,  becauie  we  are  more  in- 
dined  to  exert  the  mufcles  fublervient  to  maftication  from  their 
early  obedience  to  violent  efforts  of  volition. 

But  in  the  cafe  related  in  SeX.  XIX.  on  Reverie,  the  cata- 
leptic lady  had  pain  in  her  upper  teeth ; and  preffing  one  of  her 
hands  vehemently  againfl  her  cheek-bone  to  diminiih  this  pain, 
it  remained  in  that  attitude  for  about  half  an  hour  twice  a dav, 
till  the  painful  paroxyfm  was  over. 

I have  this  very  day  feen  a young  lady  in  this  difeafe  (with 
which  {he  has  frequently  been  affliXed) ; fhe  began  to-day  with 
violent  pain  lhooring  from  one  fide  of  the  forehead  to  the  occiput, 
and  after  various  druggies  lay  on  the  bed  with  her  fingers  and 
wrifts  bent  and  feifr  for  about  two  hours;  in  other  reipeXs  fhe 
feemed  in  a fyncope  with  a natural  pulfe.  She  then  had  inter- 
vals of  pain  and  of  fpafm,  and  took  three  grains  of  opium  every 
hour  till  fhe  had  taken  nine  grains,  before  the  pains  and  fpafm 
ceafed. 

There  is,  however,  another  fpecies  of  fixed  fpafm,  which 
differs  from  the  former,  as  the  pain  exifts  in  the  contraXed 
tnufcle,  and  would  leern  rather  to  be  the  confequence  than  the 
caufe  of  the  contraXion,  as  in  the  cramp  in  the  calf  of  the 
leg,  and  in  many  other  parts  of  the  body. 

In  thefe  fpafms  it  fhould  feem,  that  the  mufcle  itfelf  is  firiT 
thrown  into  contraXion  by  fome  difagreeable  lenfation,  as  ot 
cold  ; and  that  then  the  violent  pain  is  produced  by  the  great 
contraXion  of  the  mufcular  fibres  extending  its  own  tendons, 
which  are  laid  to  be  fenlible  to  extenfion  only  ; and  is  further 
explained  in  SeX.  XVIil.  15. 

6.  Many 


Sect.  XXXIV.  i.  DISEASES  OF  VOLITION.  31^ 

6.  Many  inftances  have  been  given  in  this  work,  where,  after 
violent  motions,  excited  by  irritation,  the  organ  has  become 
quiefcent  to  lefs,  and  even  to  the  great  irritation,  which  induced 
it  into  violent  motion ; as  after  looking  long  at  the  fun  or  any 
bright  colour,  they  ceafe  to  be  feen ; and  after  removing  from 
bright  day-light  into  a gloomy  room,  the  eye  cannot  at  firft  per- 
ceive the  objedts  which  ftimulate  it  lefs.  Similar  to  this  is.  the 
fyncope,  which  fucceeds  after  the  violent  exertions  of  our  volun- 
tary motions,  as  after  epileptic  fits  ; for  the  power  of  volition 
adts  in  this  cafe  as  the  fiimulus  in  the  other.  This  fyncope  is 
a temporary  palfy,  or  apoplexy,  which  ceafes  after  a time,  the 
mufcles  recovering  their  power  of  being  excited  into  action  by 
the  efforts  of  volition;  as  the  eye,  in  the  circumftance  above 
mentioned,  recovers  in  a little  time  its  power  of  feeing  objedts  in 
a gloomy  room,  which  were  inviiible  immediately  after  com- 
ing out  of  a ftronger  light.  This  is  owing  to  an  accumula- 
tion of  fenforial  power  during  the  inadtion  of  thofe  fibres  which 
were  before  accuftomed  to  perpetual  exertions,  as  explained  in 
Sedt.  XII.  7.1.  Aflighter  degree  of  this  difeafe  is  experienced 
by  every  one  after  great  fatigue,  when  the  mufcles  gain  fuch 
inability  to  further  adtion,  that  we  are  obliged  to  reft  them  for 
a while,  or  to  fummon  a greater  power  of  volition  to  continue 
their  motions. 

In  all  the  fyncopes  which  I have  feen  induced  after  convul- 
five  fits,  the  pulfe  has  continued  natural,  though  the  organs  of 
fenfe,  as  well  as  the  locomotive  mufcles,  have  ceafed  to  perform 
their  functions  ; for  it  is  neceffary  for  the  perception  of  objedts, 
that  the  external  organs  of  fenfe  fhould  be  properly  excited  by 
the  voluntary  power,  as  the  eyeftids  rauft  be  open,  and  perhaps 
the  mufcles  of  the  eye  put  into  adtion  to  diftend,  and  thence 
give  greater  pellucidity  to  the  cornea,  which  in  fyncope,  as  in 
death,  appears  flat  and  lefs  tranfparent.  The  tympanum  of  the 
ear  alfo  feems  to  require  a voluntary  exertion  of  its  mufcles,  to 
gain  its  due  tenfion ; and  it  is  probable  the  other  external  organs 
of  fenfe  require  a fimilar  voluntary  exertion  to  adapt  them  to 
the  diftindl  perception  of  objedts.  Hence,  in  fyncope,  as  in  fleep, 
as  the  power  of  volition  is  fufpended,  no  external  objects  are 
perceived.  See  Sedt.  XVIII.  5.  During  the  time  which  the 
patient  lies  in  a fainting  fit,  the  fpirit  of  animation  becomes  ac- 
cumulated ; and  hence  the  mufcles  in  a while  become  irritable 
by  their  ufual  ftimulation,  and  the  fainting  fit  ceafes.  See  Sedt. 
XII.  7.  I. 

7.  If  the  exertion  of  the  voluntary  motions  has  been  ftill 
more  energetic,  the  quiefcence  which  fucceeds,  is  fo  complete, 
that  they  cannot  again  be  excited  into  action  by  the  efforts  of 

T t the 


$t6-  DISEASES  OF  VOLITION.  Sect.  XXXIV.  r. 

the  will,  In  this  manner  the  palfy  and  apoplexy  (which  is  an 
univerfal  pally)  are  frequently  produced  after  convulfions,  or 
other  violent  exertions : of  this  I fhall  add  a few  inftances. 

Platernus  mentions  fome  who  have  died  apoplectic  from 
violent  exertions  in  dancing ; and  Dr.  Mead,  in  his  Effay  on 
Poifons,  records  a patient  in  the  hydrophobia,  who  at  one  ef- 
fort broke  the  cords  which  bound  him,  and  at  the  fame  inftant 
expired.  And  it  is  probable,  that  thofe  who  have  expired  from 
immoderate  laughter,  have  died  from  this  paralylis  confequent 
to  violent  exertion.  Mrs.  Scott,  of  Stafford,  was  walking  in 

her  garden  in  perfect  health,  with  her  neighbour  Mrs. ; the 

latter  accidentally  tell  into  a muddy  rivulet,  and  tried  in  vain  to 
difengage  herfelt  by  the  affiftance  of  Mrs.  Scott’s  hand.  Mrs, 
Scott  exerted  her  utmoft  power  for  many  minutes,  firft  to  affilt 
her  friend,  and  next  to  prevent  herfelf  from  being  pulled  into 
the  morafs,  as  her  diftreffed  companion  would  not  difengage 
her  hand.  After  other  affiftance  was  procured  by  their  united 
fcreams,  Mrs.  Scott  walked  to  a chair  about  twenty  yards  from 
the  brook,  and  was  feized  with  an  apopledtic  ftroke  ; which 
continued  many  days,  and  terminated  in  a total  lofs  of  her  right 
arm,  and  her  fpeech  ; neither  of  which  Hie  ever  after  perfectly 
recovered , 

It  is  faid,  that  many  people  in  Holland  have  died  after  Ikat- 
ing  too  long  or  too  violently  on  theft  frozen  canals ; it  is  pro- 
bable the  death  of  thefe,  and  of  others,  who  have  died  fudden- 
ly  in  fwimming,  has  been  owing  to  this  great  quiefcence  or  pa- 
ralylis  ; which  has  fucceeded  very  violent  exertions,  added  to 
the  concomitant  cold,  which  has  had  greater  eft'eSt  after  the  fuf- 
ferers  had  been  heated  and  exhaufted  by  previous  exercife. 

I remember  a young  man  of  the  name  of  Nairne,  at  Cam- 
bridge, who,  walking  on  the  edge  of  a barge,  fell  into  the  river. 
H iscoufin  and  lellow-ftudent  of  the  fame  name,  knowing  the 
other  could  not  fwim,  plunged  into  the  water  after  him,  caught 
him  by  his  clothes,  and,  approaching  the  bank,  by  a vehement 
exertion  propelled  him  fafe  to  the  land  ; hut  that  inftant,  leized, 
as  was  fuppofed,  by  the  cramp,  or  paralylis,  funk  to  rife  no 
more.  The  realon  why  the  cramp-  ot  the  mufdes,  which  com- 
pofe  the  calf  ot  the  leg,  is  lo  liable  to  affedt  fwimmers,  is,  be- 
caufe  thefe  mufetes  have  very  weak  antagonifts,  and  are  in 
walking  generally  elongated  again  after  their  contraction  bv 
the  weight  of  the  body  on  the  ball  ot  the  toe,  which  is  very 
much  greater  than  the  refiftance  ot  the  water  in  lwimming. 
See  Section  XVIII.  15. 

It  does  not  follow,  that  every  apoplectic  or  paralytic  attack 
is  immediately  preceded  by  vehement  exertion;  die  quiefcence, 

which. 


Sect.  XXXIV.  i.  DISEASES  OF  VOLITION.  317 

which  fucceeds  exertion,  and  which  is  not  fo  great  as  to  be 
termed  paralyhs,  frequently  recurs  afterwards  at  certain  periods ; 
and  by  other  caufes  of  quiefcence,  occurring  with  thofe  peri- 
ods, as  was  explained  in  treating  of  the  paroxyfms  of  intermit- 
ting fevers  ; the  quiefcence  at  length  becomes  fo  great  as  to  be 
incapable  of  again  being  removed  by  the  efforts  of  volition,  and 
^complete  paralyfis  is  formed.  See  Sedfion  XXXII.  3.  2. 

Many  of  the  paralytic  patients,  whom  I have  leen,  have 
evidently  had  difeafed  livers  from  the  too  frequent  potation  of 
fpirituous  liquors  ; fome  of  them  have  had  the  gutta  rofea  on 
their  faces  and  breafts ; which  has,  in  fome  degree,  receded 
-either  fpontaneoufly,  or  by  the  ufe  of  external  remedies,  and 
the  paralytic  ftroke  has  fucceeded;  and  as  in  feveral  perfons, 
who  have  drank  much  vinous  fpirits,  I have  obferved  epileptic 
fits  to  commence  at  about  forty  or  fifty  years  of  age,  without 
any  hereditary  taint,  from  the  ftimulus,  as  I believed,  of  a dif- 
eafed liver : I was  induced  to  afcribe  many  paralytic  cafes  to 
the  fame  fource,  which  were  not  evidently  the  effect  of  age, 
or  of  unacquired  debility.  And  the  account  given  before  of 
dropfies,  which  very  frequently  are  owing  to  a paralyfis  of  the 
abforbent  fyftem,  and  are  generally  attendant  on  free  drinkers 
of  fpirituous  liquors,  confirmed  me  in  this  opinion. 

The  difagreeable  irritation  of  a difeafed  liver  produces  exer- 
tions and  confequent  quiefcence  ; thefe,  by  the  accidental  con- 
currence of  other  caufes  of  quiefcence,  as  cold,  folar  or  lunar 
periods,  inanition,  the  want  of  their  ufual  portion  of  fpirit  of 
wine,  at  length  produces  paralyfis. 

This  is  further  confirmed  by  obferving,  that  the.mufcles  we 
moft  frequently  or  mod  powerfully  exert,  are  moff  liable  to 
palfy,  as  thofe  of  the  voice  and  of  articulation  ; and  of  thofe 
paralytics  which  I have  feen,  a much  greater  proportion  have 
loft  the  ufe  of  their  right  arm,  which  is  fo  much  more  general- 
ly exerted  than  the  left. 

I cannot  difmifs  this  fubjedt  without  obferving,  that  after  a 
paralytic  ftroke,  if  the  vital  powers  are  not  much  injured,  that 
the  patient  has  all  the  movements  of  the  affedted  limb  to  learn 
over  again,  juft  as  in  early  infancy : the  limb  is  firft  moved  by 
the  irritation  of  its  mufcles,  as  in  fixetching,  (of  which  a cafe 
was  related  in  Sedtion  VII.  1,  3.)  or  by  the  eledtric  concuffion ; 
afterwards  it  becomes  obedient  to  fenfation,  as  in  violent  dan- 
ger or  fear ; and  laftly,  the  mufcles  become  again  affoeiated 
with  volition,  and  gradually  acquire  their  ufual  habits  of  adt- 
ing  together. 

Another  phenomenon  in  palfies  is,  that  when  the  limbs  of 
one  fide  are  difabled  thofe  of  the  other  are  in  a perpetual  motion. 

This 


3i8  DISEASES  OF  VOLITION.  Sect.  XXXIV.  2. 

This  can  only  be  explained  from  conceiving  that  the  power  of 
motion,  whatever  it  is,  or  wherever  it  refides,  and  which  is  capa- 
ble ot  being  exhaufted  by  fatigue,  and  accumulated  in  reft,  is 
now  lefs  expended,  whilft  one  half  of  the  body  is  incapable  of 
receiving  its  ufual  proportion  of  it,  and  is  hence  derived  with 
greater  eafe,  or  in  greater  abundance,  into  the  limbs,  which 
remain  unaffedted. 

II.  1.  The  excefs  or  defedt  of  voluntary  exertion  produces 
fimilar  efFedts  upon  the  fenfual  motions,  or  ideas  of  the  mind, 
as  thofe  already  mentioned  upon  the  mufcular  fibres.  Thus, 
when  any  violent  pain,  arifmg  from  the  defedt  of  fome  pecu- 
liar ftimulus,  exifts  either  in  the  mufcular  or  fenfual  fyftems 
of  fibres,  and  which  cannot  be  removed  by  acquiring  the  de- 
fedlive  ftimulus;  as  in  fome  conftitutions  convulfions  of  the 
mufcles  are  produced  to  procure  a temporary  relief,  fo  in 
other  conftitutions  vehement  voluntary  exertions  of  the  ideas  of 
tire  mind  are  produced  for  the  fame  purpofe  ; for  during  this  ex- 
ertion, like  that  of  the  mufcles,  the  pain  either  vanishes  or  is  • 
diminifhed:  this  violent  exertion  conftitutes  madnefs;  and  in 
many  cafes  I have  feen  the  madnefs  take  place,  and  the  convul- 
fions ceafe,  and  reciprocally  the  madnefs  ceafe,  and  the  convul- 
fions fupervene.  See  Sedition  III.  5.  8. 

2.  Madnefs  is  diftinguifhable  from  delirium,  as  in  the  latter 
the  patient  knows  not  the  place  where  he  refides,  nor  the  perfons  - 
of  his  friends  or  attendants,  nor  is  confcious  of  any  external  ob- 
jcdts,  except  when  fpoken  to  with  a louder  voice,  or  ftimulated 
with  unufual  force,  and  even  then  he  foon  relapfes  into  a ftate 
of  inattention  to  every  thing  about  him  : whilft  in  the  former 
he  is  perfedfly  fenfible  to  every  thing  external,  but  has  the  volun- 
tary powers  of  his  mind  intenfely  exerted  on  fome  particular 
objedt  of  his  defire  or  averfion ; he  hai  hours  in  his  thoughts  a 
iulpicion  ol  all  mankind,  left  they  ftrould  counteradi  his  defigns ; 
and  while  he  keeps  his  intentions,  and  the  motives  ot  his  adtions 
profoundly  fecret,  he  is  perpetually  ftudying  the  means  of  ac- 
quiring die  objedt  of  his  with,  or  of  preventing  or  revenging 
the  injuries  he  fulpedts. 

3.  A late  French  philofopher,  Mr.  Helvetius,  has  deduced 
almoft  all  our  adtions  from  this  principle  of  their  relieving  us 
from  the  ennui  or  tardium  vitae ; and  true  it  is,  that  our  detires 
01  averfions  are  the  motives  of  ali  our  voluntary  adtions;  and 
human  nature  feems  to  excel  other  animals  in  the  more  facile ute 
of  this  voluntary  power,  and  on  that  account  is  more  liable  to 
infanity  than  other  animals.  But  in  mania  this  violent  exertion 
of  volition  is  expended  on  miftaken  objedts,  and  would  not  be 
relieved,  though  we  were  to  gain  or  elcape  the  objedts  that  ex- 
cite 


Sect.  XXXIV.  2.  DISEASES  OF  VOLITION.  319 

cite  it.  Thus  I have  feen  two  indances  of  madmen,  who  con- 
ceived that  they  had  the  itch,  and  feveral  have  believed  they  had 
the  venereal  infection,  without  in  reality  having  a fymptom  of 
either  of  them.  They  have  been  perpetually  thinking  upon 
this  fubie£t,  and  fome  of  them  were  in  vain  falivated  with  de- 
fign  of  convincing  them  to  the  contrary. 

4.  In  the  minds  of  mad  people  thole  volitions  alone  exid, 
which  are  unmixed  with  fenfation;  immoderate  fufpicion  is 
generally  the  hid  fymptom,  and  want  of  fhame,  and  want  of 
delicacy  about  cleanlinefs.  Sufpicion  is  a voluntary  exertion  of 
the  mind  arihng  from  the  pain  of  tear,  which  it  is  exerted  to  re- 
lieve : fhame  is  the  name  of  a peculiar  difagreeable  fenfation, 
fee  Fable  ot  the  Bees  ; and  delicacy  about  cleanlinefs  arifes  from 
another  difagreeable  fenfation : and  therefore  are  not  found  in 
the  minds  of  maniacs,  which  are  employed  folely  in  voluntary 
exertions.  Hence  the  mod  moded  women  in  this  difeafe  walk 
naked  amongd  men  without  any  kind  of  concern,  ufe  obfcene 
difcourfe,  and  have  no  delicacy  about  their  natural  evacuations. 

5.  Nor  are  maniacal  people  more  attentive  to  their  natural 
appetites,  or  to  the  irritations  which  furround  them,  except  as 
far  as  may  refpedt  their  fufpicions  or  defigns ; for  the  violent 
and  perpetual  exertions  of  their  voluntary  powers  of  mind  pre- 
vents their  perception  of  almod  every  other  objedt,  either  of 
irritation  or  of  fenfation.  Hence  it  is  that  they  bear  cold,  hun- 
ger, and  fatigue,  with  much  greater  pertinacity  that  in  their 
fober  hours,  and  are  lefs  injured  by  them  in  that  refpedt  to  their 
general  health.  Thus  it  is  aiTerted  by  hidorians,  that  Charles 
the  Twelfth  of  Sweden  ilept  on  the  fnow,  wrapped  only  in  his 
cloak,  at  the  fiege  of  Frederickdad,  and  bore  extremes  of  cold, 
and  hunger,  and  fatigue,  under  which  numbers  of  his  foldiers 
periihed;  becaufe  the  king  was  infane  with  ambition,  but  the 
foldier  had  no  fuch  powerful  dimulus  to  preferve  his  fydem 
from  debility  and  death. 

6.  Beddes  the  infancies  arifmgfrom  exertions  in  confequence 
of  pain,  there  is  alfo  a pleafureable  infanity,  as  well  as  a plca- 
fureable  delirium ; as  the  infanity  of  perfonal  vanity,  and  that 
of  religious  fanaticifm.  When  agreeable  ideas  excite  into  mo- 
tion the  fenforial  power  of  fenfation,  and  this  again  caufes  other 
trains  of  agreeable  ideas,  a condant  dream  of  pleafureable  ideas 
fucceeds,  and  produces  pleafureable  delirium.  So  when  the 
fenlorial  power  of  volition  excites  agreeable  ideas,  and  the  plea- 
fure  thus  produced  excites  more  volition  in  its  turn,  a condant 
flow  of  agreeable  voluntary  ideas  fucceeds ; which,  when  thus 
exerted  in  the  extreme,  conditutes  infanity. 

"I  nus,  when  our  mufcular  actions  are  excited  by  ourfenfations 

of 


32o  DISEASES  OF  VOLITION.  Sect.  XXXIV.  2. 

of  pleafure,  it  is  termed  play ; when  they  are  excited  by  our  vo- 
lition, it  is  termed  work ; and  the  former  of  thefe  is  attended 
withlefs  fatigue,  becaufe  the  mufcular  adtions  in  play  produce 
in  their  turn  more  pleafureable  fenfation ; which  again  has  the 
property  of  producing  more  mufcular  acStion.  An  agreeable 
inftance  of  this  I faw  this  morning.  A little  boy,  who  was 
tired  with  walking,  begged  of  his  papa  to  carrv  him.  “ Here,” 
fays  the  reverend  dodtor,  “ ride  upon  my  gold-headed  cane,” 
and  the  plealed  child,  putting  it  between  his  legs,  gailopped  away 
with  delight,  and  complained  no  more  of  his  fatigue.  Here  the 
aid  of  another  ienforial  power,  that  of  pleafureable  fenfation, 
fuperadded  vigour  to  the  exertions  of  exhaufred  volition  ; 
which  could  otherwife  only  have  been  excited  by  additional 
pain,  as  by  the  lath  of  fiavery.  On  this  account,  where  the 
whole  fenforial  power  has  been  exerted  on  the  contemplation 
of  the  promifed  joys  of  heaven,  the  faints  of  all  perfecuted  reli- 
gions have  borne  the  tortures  of  martyrdom  with  otherwife  uiu 
accountable  firmnefs. 

7.  There  are  fome  difeafes,  which  obtain  at  leaft  a temporary 
relief  from  the  exertions  of  infanity  ; many  inflances  of  dropfles 
being  thus  for  a time  cured  are  recorded.  An  elderlv  woman 
labouring  wdth  afeites,  I tw  ice  faw  relieved,  for  fome  weeks,  bv 
infanity;  thedropfy  ceafed  for feveral  weeks,  and  recurred  again, 
alternating  wdth  the  infinity.  A man  afflicted with  difficult 
refpiration  on  lying  down,  with  very  irregular  pulfe,  and  cede- 
matous  legs,  whom  I faw  this  day,  has  for  above  a week  been 
much  relieved  in  refpedt  to  all  thofe  fymptoms  by  the  acceffion 
of  infanity,  which  is  lliewn  by  inordinate  fufpicion,  and  great 
anger. 

in  cafes  of common  temporary  anger  theincreafed  adtion  of 
the  arterial  fyflem  is  feen  by  the  red  lkin,  and  increafed  pu!lc, 
with  the  immediate  increafe  of  mufcular  adtivity.  A friend  of 
mine,  when  he  was  painfully  fatigued  by  riding  on  horfeback, 
was  accuftomed  to  call  up  ideas  into  his  mind,  which  ufed  to 
excite  his  anger  or  indignation,  and  thus  for  a time  at  leaft  re- 
lieved the  pain  of  fatigue.  By  this  temporary  infanity,  the  effect 
of  the  voluntary  power  upon  the  whole  of  his  fyftem  was  in- 
creafed ; as  in  cafes  of  droply  above  mentioned,  it  would  appear 
that  the  increafed  adtion  of  the  voluntary  faculty  of  the  fenfo- 
rium  affedted  the  abforbent  fyftem,  as  well  as  the  feceming  one. 

8.  In  refpedt  to  relieving  inflammatory  pains,  and  removing 
fever,  I have  feen  many  inflances,  as  mentioned  in  Sedt.  XII. 
2.  4.  One  lady  whom  1 attended,  had  twice,  at  fome  years 
interval,  a locked  jaw,  which  relieved  a pain  on  her  fternum 
with  peripneumeny.  Two  other  ladies  1 faw,  who,  towards 


Sect.  XXXIV.  3.  DISEASES  OF  VOLITION'.  321 

the  end  of  violent  peripneumony,  in  which  they  frequently  loft 
blood,  were  at  length  cured  by  infanity  fupervening.  In  the  for- 
mer the  increafed  voluntary  exertion  of  the  mufcles  of  the  jaw, 
in  the  latter  that  of  the  organs  of  fenfe,  removed  the  difeafe ; 
that  is,  the  difagreeable  fenfation  which  had  produced  the  in- 
flammation, now  excited  the  voluntary  power,  and  thefe  new 
voluntary  exertions  employed  or  expended  the  fuperabundant 
fenforial  power,  which  had  previoufly  been  exerted  on  the 
arterial  fyftem,  and  caufed  inflammation. 

Another  cafe,  which  I think  worth  relating,  was  of  a young 
man  about  twenty  ; he  had  laboured  under  an  irritative  fever, 
with  debility,  for  three  or  four  weeks,  with  very  quick  and 
very  feeble  pulfe,  and  other  ufual  fymptoms  of  that  ipecies  of 
typhus  ; but  at  this  time  complained  much  and  frequen  ly  of 
■pain  of  his  legs  and  feet.  When  thofe  who  attended  him  were 
nearly  in  defpair  of  his  recovery,  I obferved  with  pleafure  an 
infanity  of  mind  fupervene  ; which  was  totally  different  from 
delirium,  as  he  knew  his  friends,  calling  them  by  their  names, 
and  the  room  in  which  he  lay,  but  became  violently  fufpicious 
of  his  attendants,  and  calumniated  with  vehement  oaths  his 
tender  mother,  who  fat  weeping  by  his  bed.  On  this  his  pulfe 
became  flower  and  firmer,  but  the  quicknefs  did  not  for  fome 
time  entirely  ceafe,  and  he  gradually  recovered.  In  this  cafe 
the  introduction  of  an  increafed  quantity  of  the  power  of  vo- 
lition gave  vigour  to  thofe  movements  of  the'fyfiem,  which  are 
generally  only  aCtuated  by  the  power  of  irritation,  and  of  af- 
iociation. 

Another  cafe  I recoiled  of  a young  man,  about  twenty- 
five,  who  had  the  fcarlet  fever,  with  very  quick  pulfe.  and  an 
univerfal  eruption  on  his  fkin,  and  was  not  without  reafoa 
elteemed  to  be  in  great  danger  of  his  life.  After  a few  days  an 
infanity  fupervened,  which  his  friends  mifcook  for  delirium-, 
and  he  gradually  recovered,  and  the  cuticle  peeled  off.  From 
thefe  and  a few  other  cafes  I have  always  efleemed  infanity  to 
be  a favourable  fign  in  fevers,  and  have  cautioufly  diftinguiihed 
it  from  delirium. 

III.  Another  mode  of  mental  exertion  to  relieve  pain,  is  by 
producing  a train  of  ideas  not  only  by  die  efforts  of  volition, 
as  in  infanity,  but  by  thofe  of  fenfation  likewile,  as  in  delirium 
and  fleep.  This  mental  effort  is  termed  reverie,  or  fomnam- 
buiation,  and  is  defcribed  more  at  large  in  Sect.  XIX.  on  that 
iubjed.  But  I lhall  here  relate  another  cafe  of  that  wonder- 
ful difeafe,  which  fell  yefteiday  under  my  eye,  and  to  which  I 
have  ieen  many  analogous  alienations  of  mind,  though  not  ex- 
actly iimilar  in  all  ciicumftances.  But  as  all  of  them  either 

becan 


322  DISEASES  OF  VOLITION.  Sect.  XXXIV.  j. 

began  or  terminated  with  pain  or  convulfiori,  there  can  be  no 
doubt  but  that  they  are  of  epileptic  origin,  and  conftitute  ano- 
ther mode  of  mental  exertion  to  relieve  fome  painful  fenfation. 

1.  Mafter  A.  about  nine  years  old,  had  been  feized  at  leven 
every  morning  for  ten  days  with  uncommon  fits,  and  had  flight 
returns  in  the  afternoon.  They  were  fuppofed  to  originate 
from  worms,  and  had  been  in  vain  attempted  to  be  removed  bv 
vermifuge  purges.  As  his  fit  wras  expected  at  feven  yefterdav 
morning,  I faw  him  before  that  hour ; he  w>as  afleep,  feemed 
free  from  pain,  and  his  pulfe  natural.  About  feven  he  began 
to  complain  of  pain  about  his  navel,  or  more  to  the  left  fide, 
and  in  a few  minutes  had  exertions  ot  his  arms  and  legs  like 
fwimming.  He  then  for  half  an  hour  hunted  a pack  ot  hounds ; 
as  appeared  by  his  hallooing,  and  calling  the  dogs  bv  their 
names,  and  difeourfing  with  the  attendants  of  the  chafe,  deferib- 
ing  exadfly  a day  of  hunting,  which  (I  was  informed)  he  had 
witneffed  a year  before,  going  through  all  the  moll  minute  cir- 
cumflances  of  it ; calling  to  people,  who  were  then  prefent, 
and  lamenting  the  abfence  of  others,  who  were  then  alfo  ab- 
fent.  After  this  feene  he  imitated,  as  he  lay  in  bed,  fome  of 
the  plays  of  boys,  as  fwimming  and  jumping.  He  then  lung 
an  Englifh  and  then  an  Italian  long;  part  of  which  with  his 
eyes  open,  and  part  with  them  clofed,  but  could  not  be  awakened 
or  excited  by  any  violence  which  it  was  proper  to  ufe. 

After  about  an  "hour  he  came  fuddenly  to  himfelt  with  ap- 
parent furprife,  and  feemed  quite  ignorant  of  any  part  of  what 
had  paflfed ; and  after  being  apparently  well  tor  half  an  hour, 
he  fuddenly  fell  into  a great  ftupor,  with  flower  pulle  than  na- 
tural, and  a flow  moaning  refpiration,  in  which  he  continued 
about  another  half  hour,  and  then  recovered. 

The  fequel  of  this  difeafe  was  favourable;  he  was  di reified 
one  grain  of  opium  at  fix  every  morning,  and  then  to  rile  out 
of  bed ; at  half  part  fix  he  was  diredfed  fifteen  drops  of  lauda- 
num in  a glafs  ot  wine  and  water.  The  firft  day  the  paroxyfin 
became  fhorter,  and  lefs  violent.  The  dole  of  opium  was  ira- 
creafed  to  one-half  more,  and  in  three  or  tour  days  the  fits  left 
him.  The  bark  and  filings  of  iron  were  alfo  exhibited  twice 
a day  ; and  I believe  the  complaint  returned  no  more. 

2.  In  this  paroxyfin  it  muff  be  obierved,  that  he  began  with 
pain,  and  ended  with  ftupor,  in  both  circumftances  relembiing 
a fit  of  epilepfy.  And  that  therefore  the  exertions  both  ot  muni 
and  body,  both  the  voluntary  ones,  and  thole  immediatelv  excit- 
ed by  pleafureable  fenfation,  were  exertions  to  relieve  pain. 

The  hunting  feene  appeared  to  be  rather  an  act  of  memory 
than  of  imagination,  and  was  therefore  rather  a voluntary  ex- 
ertion, 


Sect.  XXXIV.  3.  DISEASES  OF  VOLITION. 


323 


ertion,  though  attended  with  the  pleafureable  eagernefs  which 
was  the  confequence  of  thofe  ideas  recalled  by  recollection, 
and  not  thecaufe  of  them. 

Thefe  ideas  thus  voluntarily  recollected  were  fucceeded  by 
fenfations  of  pleafure,  though  his  fenfes  were  unaffected  by 
the  itimuli  of  vifible  or  audible  objects  ; or  fo  weakly  excited 
by  them  as  not  to  produce  fenfation  or  attention.  And  the 
pleafure  thus  excited  by  volition  produced  other  ideas  and  other 
motions  in  confequence  of  the  fenforial  power  of  fenfation. 
Whence  the  mixed  catenations  of  voluntary  and  fenfitive  ideas 
and  mufcular  motions  in  reverie  ; which,  like  every  other  kind 
of  vehement  exertion,  contribute  to  relieve  pain,  by  expend- 
ing a large  quantity  of  fenforial  power. 

Thofe  fits  generally  commence  during  lleep,  from  whence 
I fuppofe  they  have  been  thought  to  have  fome  connection 
with  fleep,  and  have  thence  been  termed  Somnambalifm  ; but 
their  commencement,  during  fleep,  is  owing  to  our  increafed 
excitability  by  internal  fenfations  at  that  time,  as  explained  in 
Sect.  XVIII.  14.  and  15.  and  riot  to  any  fimilitude  between 
reverie  and  fleep. 

3.  I was  once  concerned  for  a very  elegent  and  ingenious 
young  lady,  who  had  a reverie  on  alternate  days,  which  con- 
tinued nearly  the  whole  day  ; and  as  in  her  days  of  difeafe  fhe 
took  up  the  fame  kind  of  ideas  which  fhe  had  converfed  about 
on  the  alternate  day  before,  and  could  recollect  nothing  of  them 
on  her  well-day,  fhe  appeared  to  her  friends  to  poffefs  two 
minds.  This  cafe  alfo  was  ot  epileptic  kind,  and  was  cured, 
with  fome  relapfes,  by  opium  adminiftered  before  the  com- 
mencement of  the  paroxyfm. 

4.  Whence  it  appears,  that  the  method  of  relieving  in- 
flammatory pains,  is  by  removing  all  ffimulus,  as  by  venefec- 
tion,  cool  air,  mucilaginous  diet,  aqueous  potation,  filence, 
darknefs. 

The  method  of  relieving  pain  from  defect  of  ffimulus  is  by 
fupplying  the  peculiar  ffimulus  required,  as  of  food  or  warmth. 

And  the  general  method  of  relieving  pain  is  by  exciting  into 
action  fome  great  part  of  the  fyftem,  for  the  purpofe  of  expend- 
ing a part  of  the  fenforial  power.  This  is  done  either  by  ex- 
ertion of  the  voluntary  ideas  and  mufcles,  as  in  infanity  and 
convulfions  ; or  by  exerting  both  voluntary  and  fenfitive  mo- 
tions, as  in  reverie  ; or  by  exciting  the  irritative  motions  bv 
wine  or  opium  internally,  and  by  the  warm  bath  or  blifters 
externally  ; or  laftlv,  by  exciting  the  fenfitive  ideas  by  good 
news,  affecting  ftories,  or  agreeable  paflions. 


Uu 


SECT. 


324  DISEASES  OF  ASSOCIATION.  Sect.  XXXV.  i. 

SECT.  XXXV. 

DISEASES  OF  ASSOCIATION. 

I.  X.  Sympathy  or  confent  of  parts.  Primary  and  [econdary 
parts  of  an  affociated  train  of  motions  reciprocally  affecl 
each  other.  Parts  of  irritative  trains  of  motion  ajfelf 
each  other  in  four  ways.  Sympathies  of  the  fkin  and  Jlo- 
mach.  Flufiing  of  the  face  after  a meal.  Eruption  of  the 
[mall-pox  on  the  face.  Chilnefs  after  a meal.  2.  Vertigo 
from  intoxication.  3.  Abforp  on  from  the  lungs  and  peri- 
cardium by  emetics.  In  vomiting  the  affions  op  the fomach 
are  decreajed , not  increajcd.  Digejhon  Jlrengthcned  after 
an  emetic.  Vomiting  from  deficiency  of  [enforial  power , 
4.  Dyfpncea  from  cold  bathing.  Slow pulfe  from  digitalis. 
Death  from  gout  in  the  Jiomach.  II.  I.  Primary  and  fe~ 
condary  parts  of  jenfitive  affociations  afield  each  other. 
Pain  from  gall-Jlone  ; from  urinary  Jlone.  Hemicrania. 
Painful  epilepfy.  2.  Gout  and  red  face  from  inflamed 
liver.  Shingles  from  inflamed  kidney.  3.  Coryza  from 

cold  applied  to  the  feet.  Pleurijy.  Hepatitis.  4.  Pain 
of  Jhoulders  from  inflamed  liver.  III.  Di [cafes  from  the 
affociations  of  ideas. 

I.  1.  MANY  fynchronous  and  fucceffive  motions  of  our 
mufcular  fibres,  and  of  our  organs  of  fenfe,  or  ideas,  become 
affociated  fo  as  to  form  indiffoluble  tribes  or  trains  or  action,  as 
fhewn  in  Sedlion  X.  on  AfTociate  Motions.  Some  conflitu- 
tions  more  eafily  eftablifh  thefe  affociations,  whether  by  vo- 
luntary, fenfitive,  or  irritative  repetitions,  and  fome  more  eafily 
lofe  them  again,  as  fhewn  in  Section  XXXI.  on  Tempera- 
ments. 

When  the  beginning  of  fuch  a train  of  actions  becomes  by 
any  means  difordered,  the  fucceeding  part  is  liable  to  become 
difturbed  in  confequence,  and  this  is  commonly  termed  fympa- 
thy  or  confent  of  parts,  by  the  writers  of  medicines.  For  the 
more  clear  underftanding  of  thefe.  fympathies,  we  muft  confi- 
der  a tribe  or  train  of  actions  as  divided  into  two  parts,  and  call 
one  of  them  the  primary  or  original  motions,  and  die  other  the 
fecondary  or  fympathetic  ones. 

The  primary  and  fecondary  parts  of  a train  of  irritative  ac- 
tions may  reciprocally  affedl  each  other  in  four  different  man- 
ners. 1.  They  may  both  be  exerted  with  greater  energy  than 
natural.  2.  The  former  may  a£t  with  greater,  and  the  latter 
with  lels  energy.  3.  The  former  may  act  with  lefs,  and  the 

latter 


Sect.  XXXV.  i.  DISEASES  OF  ASSOCIATION.  325 

latter  with  greater  energy.  4.  They  may  both  ail  with  lei's 
energy  than  natural.  I {hall  now  give  an  example  of  each 
kind  of  thefe  modes  of  ailion,  and  endeavour  to  drew,  that 
though  the  primary  and  fecondary  parts  of  thefe  trains  or  tribes 
of  motion  are  connefiled  by  irritative  affociation,  or  their  pre- 
vious habits  of  ailing  together,  as  defcribed  in  Seil.  XX,  on 
Vertigo.  Yet,  that  their  ailing  with  fimilar  or  diflimilar  de- 
grees of  energy,  depends  on  the  greater  or  I.efs  quantity  of  fen- 
iorial  power,  which  the  primary  part  of  the  train  expends  in 
its  exertions. 

The  ailions  of  the  ftomach  conftitute  fo  important  a part  of 
the  affociations  of  both  irritative  and  fenfitive  motions,  that  it 
is  faid  to  fympathize  with  almoft  every  part  of  the  body : the 
firft  example  which  I {hall  adduce  to  drew,  that  both  the  pri- 
mary and  fecondary  parts  of  a train  of  irritative  affociations  of 
motion  ail  with  increafed  energy,  is  taken  from  theconfent  of 
tire  fkin  with  this  organ.  When  the  ailion  of  the  fibres  of  the 
ftomach  is  increafed,  as  by  the  flimulus  of  a full  meal,  the  ex- 
ertions of  the  cutaneous  arteries  of  the  face  become  increafed 
by  their  irritative  affociations  with  thofe  of  the  ftomach,  and  a 
glow  or  flu  fifing  of  the  face  fucceeds.  For  the  fmall  veffels  of 
the  fkin  of  the  face  having  been  more  accuftomed  to  the  varie- 
ties of  aclion,  from  their  frequent  expofure  to  various  degrees 
of  cold  and  heat,  become  more  eafily  excited  into  increafed 
ailion,  than  thofe  of  the  covered  parts  of  our  bodies,  and 
thus  ail  with  more  energy  from  their  irritative  or  fenfitive  affo- 
ciations with  the  ftomach.  On  this  account,  in  fmall-pox,  the 
eruption,  in  confequence  of  the  previous  affeilion  of  the  fto- 
tnach,  breaks  out  a day  fooner  on  the  face  than  on  the  hands, 
and  two  days  fooner  than  on  the  trunk,  and  recedes  in  fimilar 
times  after  maturation. 

But,  fecondly,  in  weaker  conftitutions,  that  is,  in  thofe  who 
poffefs  lefs  fenforial  power,  fo  much  of  it  is  expended  in  the 
increafed  aitions  of  the  fibres  of  the  ftomach,  excited  by  the 
ftimulus  of  a meal,  that  a fenfe  of  chilnefs  fucceeds  inftead  of 
the  univerfal  glow  above  mentioned ; and  thus  the  fecondary 
part  of  the  affociated  train  of  motions  is  dim  ini  died  in  energy  in 
confequence  of  the  increafed  afilivity  of  the  primary  part  of  it. 

2.  Another  inftance  of  a fimilar  kind,  where  the  fecondary 
part  of  the  train  a£ls  with  lefs  energy  in  confequence  of  the 
greater  exertions  of  the  primary  part,  is  the  vertigo  attending 
intoxication  : in  this  circumftance  fo  much  fenforial  power  is 
expended  on  the  ftomach,  and  on  its  neareft  or  more  ftrongly 
affociated  motions,  as  thofe  of  the  fubcutaneous  veffels,  and 
probably  of  the  membranes  of  foroe  internal  vifeera,  that  the 

irritative 


326  D!SEASES;OF  ASSOCIATION.  Sect.  XXXV.  i. 

irritative  motions  of  the  retina  become  imperfectly  exerted  from 
deficiency  of  fenforial  power,  as  explained  in  Sedd.  XX.  and 
XXL  on  Vertigo  anion  Drunkennefs,  and  hence  the  {dagger- 
ing inebriate  cannot  completely  balance  himfelf  by  fuch  inJif- 
tindd  yifion. 

3.  An  inftance  of  the  third  circumftance,  where  the  pri- 
mary part  of  a train  of  irritative  motions  adds  with  lefs,  and 
the  fecondary  part  with  greater  energy,  may  be  obferved  by 
making  the  following  experiment.  If  a perfon  lies  with  his 
arms  and  Ihoulders  out  of  bed  till  thev  become  cold,  a tem- 
porary coryza  or  catarrh  is  produced,  fo  that  the  paflfage  of 
the  nofdrils  becomes  totally  obldrudded;  at  leafd  this  happens  to 
many  people;  and  then,  on  covering  the  arms  and  fhoulders, 
till  they  become  warm,  the  paffage  of  the  noldrils  ceafes  again 
to  be  obftrudded,  and  a quantity  of  mucus  is  difcharged  from 
them.  In  this  cafe  the  quiefcence  of  the  veflfels  of  the  fkin  of 
the  arms  and  fhoulders,  occafioned  by  expofure  to  cold  air, 
produces,  by  irritative  aflociation,  an  increafed  addion  of  the  vef- 
fels  of  the  membrane  ot  the  noldrils;  and  the  accumulation  of 
fenforial  power,  during  the  torpor  of  the  arms  and  fhoulders,  is 
thus  expended  in  producing  a temporary  corvza  or  catarrh. 

Another  inftance  may  be  adduced  from  the  fvmpathy  or  con- 
fent  of  the  motions  of  the  ftomach  with  other  more  diftant 
links  of  the  very  extenfive  tribes  or  trains  of  irritative  motions 
a floriated  with  them,  defcribed  in  Sedt.  XX.  on  Vertigo.  When 
the  addions  of  the  fibres  of  the  ftomach  are  diminifhed  or  in- 
verted, the  addions  of  the  abforbent  veffels,  which  take  up  the 
mucus  from  the  lungs,  pericardium,  and  other  cells  of  the  body, 
become  increafed,  and  abforb  the  fluids  accumulated  in  them 
with  greater  avidity,  as  appears  from  the  exhibition  of  foxglove, 
antimony,  or  other  emetics,  in  cafes  of  anafarca,  attended  with 
unequal  pulfe  and  difficult  refpiration. 

That  the  add  of  naufea  and  vomiting  is  a decreafed  exertion 
of  the  fibres  of  the  ftomach  may  be  thus  deduced;  when  an 
emetic  medicine  is  adminiftered,  it  produces  the  pain  of  fick- 
nefs,  as  a difagreeable  tafte  in  the  mouth  produces  the  pain  of 
naufea ; thefe  pains,  like  that  of  hunger,  or  of  cold,  or  like 
thofe  which  are  ufually  termed  nervous,  as  the  head-ach,  or 
hemicrania,  do  not  excite  the  organ  into  greater  addion ; but 
in  this  cafe  I imagine  the  pains  of  ficknefs  or  of  naufea  coun- 
teradd or  deftroy  the  pleafureable  fenfation  which  feems  ne- 
ceflary  to  digeftion,  as  ftaewn  in  Sedd.  XXIII.  I.  1.  The 
periftaltic  motions  of  the  fibres  of  the  ftomach  become  enfeebled 
by  the  want  of  this.ftimulus  of  pleafureable  fenfation,  and,  in 
poijfequence,  flop  for  a time,  and  then  become  inverted;  for 


Sect.  XXXV.  2.  DISEASES  OF  ASSOCIATION.  32? 

they  cannot  become  inverted  without  being  previoufly  flopped. 
Now,  that  this  inverfion  of  the  trains  of  motion  of  the  fibres 
of  the  ftomach  is  owing  to  the  deficiency  of  pleafureable  fenfa- 
tion,  is  evinced  from  this  circumftance,  that  a naufeous  idea 
excited  by  words,  will  produce  vomiting  as  effectually  as  a 
naufeous  drug. 

Hence  it  appears,  that  the  add  of  naufea  or  vomiting  expends 
lefs  fenforial'  power  than  the  ufual  periftaltic  motions  of  the 
ftomach  in  the  digeftion  of  our  aliment;  and  that  hence  there 
is  a greater  quantity  of  fenforial  power  becomes  accumulated 
in  the  fibres  of  the  ftomach,  and  more  of  it,  in  confequence,  to 
fpare  for  the  a£tion  of  thofe  parts  of  the  fyfletn  which  are  thus 
affociated  with  the  ftomach,  as  of  the  whole  ablorbent  feries 
of  veffels,  and  which  are  at  the  fame  time  excited  by  their 
ufual  ftimuli. 

From  this  we  can  underftand  how,  after  the  operation  of  an 
emetic,  the  ftomach  becomes  more  irritable  and  fenfible  to  the 
ftimulus  and  the  pleafure  of  food ; fince,  as  the  fenlorial  power* 
becomes  accumulated  during  the  naufea  and  vomiting,  the  di- 
geftive  power  is  afterwards  exerted  more  forcibly  for  a time. 
It  fhould,  however,  be  here  remarked,  that  though  vomiting  is 
in  general  produced  by  the  defedt  of  this  ftimulus  of  pleafure- 
able fenfation,  as  when  a naufeous  drug  is  adminiftered ; yet, 
in  long-continued  vomiting,  as  in  fea-ficknefs,  or  from  habitual 
dram -drinking,  it  arifes  from  deficiency  of  fenforial  power, 
which,  in  the  former  cafe,  is  exhaufted  by  the  increafed  exer- 
tion of  the  irritative  ideas  of  vifion,  and  in  the  latter,  by  the 
frequent  application  of  an  unnatural  ftimulus. 

4.  An  example  of  the  fourth  circumftance  above  mentioned, 
where  both  the  primary  and  fecondary  parts  of  a train  of  mo- 
tions proceed  with  energy  lefs  than  natural,  may  be  obferved  in 
the  dyfpnoea,  which  occurs  ingoing  into  a very  cold  bath,  and 
which  has  been  defcribed  and  explained  in  Seed.  XXXIJ.  3.  2. 
And  by  the  increafed  debility  of  the  pulfations  of  the  heart 
and  arteries  during  the  operation  of  an  emetic.  Secondly,  from 
the  flownefs  and  imermiffion  of  the  pulfations  of  the  heart  from 
the  inceffant  efforts  to  vomit,  occafioned  by  an  overdofe  of  di- 
gitalis. And  thirdly,  from  the  total  ftoppage  of  the  motions 
of  the  heart,  or  death,  in  confequence  of  the  torpor  of  the  fto- 
mach, when  affetfted  with  the  commencement  or  cold  parox- 
yfm  of  the  gout.  See  Sedd.  XXV.  17. 

II.  1.  The  primary  and  fecondary  parts  of  the  trains  of  fen- 
fitive  affociation  reciprocally  affedd  each  other  in  different 
manners.  1.  The  increafed  fenfation  of  the  primary  part  may 
jpeafe,  when  that  of  the  fecondary  part  commences.  2.  The 

increafed 


328  DISEASES  OF  ASSOCIATION.  Sect.  XXXV.  2. 

increafed  adlion  of  the  primary  part  may  ceafe,  when  that  of 
the  fecondary  part  commences.  3.  The  primary  part  may 
have  increafed  fenfation,  and  the  fecondary  part  increafed  ac- 
tion. 4.  The  primary  part  may  have  increafed  action,  and 
the  fecondary  part  increafed  fenfation. 

Examples  of  the  hrft  mode,  where  the  increafed  fenfation  of 
the  primary  part  of  a train  of  fenfitive  affociations  ceafes,  when 
that  of  the  fecondarv  part  commences,  are  not  unfrequent;  as 
this  is  the  general  origin  of  thofe  pains  which  continue  fome 
time  without  being  attended  with  inflammation,  fuch  as  the 
pain  at  the  pit  of  the  ftomach  from  a ffone  at  the  neck  of  the 
gall-bladder,  and  the  pain  of  ftraogury  in  the  glans  penis  from 
a ftone  at  the  neck  of  the  urinary  bladder.  In  both  thefe  cafes, 
the  part  which  is  affected  fecondarily,  is  believed  to  be  much 
more  fenfible  than  the  part  primarily  affedted,  as  defcribed  in 
the  Catalogue  of  Difeafes,  Clafs  II.  1.  1.  10.  and  IV.  2.  1.  1, 
and  IV.  2.  x.  2. 

The  hemicrania,  or  nervous  head-ach,  as  it  is  called,  when 
it  originates  from  a decaying  tooth,  is  another  difeafe  of  this 
Jcind,  as  the  pain  of  the  carious  tooth  always  ceafes  when  the 
pain  over  one  eye  and  temple  commences.  And  it  is  probable, 
that  the  violent  pains  which  induce  convulfions  in  painful  epi- 
lepfies,  are  produced  in  the  fame  manner,  from  a more  fenfible 
part  fympathizing  with  a difeafed  one  of  leff  fenfibility.  See 
Catalogue  of  Difeafes,  Clafs  IV.  2.  1.5.  and  III.  1.  1.  7. 

The  lad  tooth,  or  dens  fapientiae,  of  the  upper  jaw,  mod 
frequently  decays  firfi,  and  is  liable  to  produce  pain  over  the 
eye  and  temple  of  that  1'ide.  The  laft  tooth  of  the  under  jaw 
is  alfo  liable  to  produce  a fimilar  hemicrania,  when  it  begins 
to  decay.  When  a tooth  in  the  upper  jaw  is  the  caufe  of  the 
3iead-ach,  a llighter  pain  is  fometiines  perceived  on  the  cheek- 
bone: and  when  a tooth  in  the  lower  jaw  is  the  caufe  of 
head-ach,  a pain  fometimes  affedts  the  tendons  of  the  muffles 
of  the  neck,  which  are  attached  near  the  jaws.  But  the  clavus 
hyflericus,  or  pain  about  the  middle  of  the  parietal  bone  on  one 
fide  of  the  head,  I have  feen  produced  by  the  fecond  of  the  mo- 
lares,  or  grinders,  of  the  under  jaw,  of  whieh  I fhall  relate  the 
following  cafe.  See  Clals  II.  1.  1.4.  and  IV.  2.  1.  5. 

Mrs. , about  thirty  years  of  age,  was  feiv.ed  with  great 

pain  about  the  middle  of  the  right  parietal  bone,  which  had  con- 
tinued a whole  day  before  I faw  her,  and  was  fo  violent  as  to 
threaten  to  occafion  convulfions.  Not  being  able  to  detedf  a 
decaying  tooth,  or  a tender  one,  by  examination  with  my  eve, 
or  by  ftriking  them  with  a tea-fpoon,  and  fearing  bad  conie- 
quences  from  her  tendency  to  convuliion,  I advifed  her  to  ex- 
x tracl 


Sect.  XXXV.  2.  DISEASES  OF  ASSOCIATION.  329 

trad!  the  laft  tooth  of  the  under-jaw  on  the  affected  fide ; which 
was  done  without  any  good  effedl.  She  was  then  directed  to 
lofe  blood,  and  to  take  a brifk  cathartic  ; and  after  that  had 
operated,  about  60  drops  of  laudanum  were  given  her,  with 
large  dofes  of  bark ; by  which  the  pain  was  removed.  In 
about  a fortnight  fhe  took  a cathartic  medicine  by  ill  advice, 
and  the  pain  returned  with  greater  violence  in  the  fame  place  ; 
and,  before  I could  arrive,  as  flie  lived  30  miles  from  me, 
fhe  fuffered  a paralytic  ftroke  ; which  affedted  her  limbs  and 
her  face  on  one  fide,  and  relieved  the  pain  of  her  head. 

About  a year  afterwards  I was  again  called  to  her  on  ac- 
count of  a pain  as  violent  as  before  exactly  on  the  fame  part 
of  the  other  parietal  bone.  On  examining  her  mouth,  I found 
the  fecond  molaris  of  the  under  jaw,  on  the  fide  before  affedfed, 
was  now  decayed,  and  concluded,  that  this  tooth  had  occa- 
fioned  the  ftroke  of  the  palfy  by  the  pain  and  confequent  exer- 
tion it  had  caufed.  On  this  account  I earneftly  intreated  her 
to  allowTlie  found  molaris  of  the  fame  jaw  oppofite  to  the  de- 
cayed one  to  be  extracted ; which  was  forthwith  done,  and  the 
pain  of  her  head  immediately  ceafed,  to  the  aftonifhment  of 
her  attendants. 

In  the  cafes  above  related  of  the  pain  exifting  in  a part  dif- 
tant  from  the  feat  of  the  difeafe,  the  pain  is  owing  to  defedt  of 
the  ufual  motions  of  the  painful  part.  This  appears  from  the 
coldnefs,  palenefs,  and  emptinefs  of  the  afFedled  veffels,  or  of 
the  extremities  of  the  body  in  general,  and  from  there  being  no 
tendency  to  inflammation.  The  increafed  adlion  of  the  primary 
part  of  thefe  aflociated  motions,  as  of  the  hepatic  termination 
of  the  bile-dud!  from  the  ftimulus  of  a gall-ftone,  or  of  the 
interior  termination  of  the  urethra  from  the  ftimulus  of  a ftone 
in  the  bladder,  or  laftly,  of  a decayed  tooth  in  hemicrania, 
deprives  the  fecondary  part  of  thefe  aflociated  motions,  name- 
ly, the  exterior  terminations  of  the  bile-dud!  or  urethra,  or  the 
pained  membranes  of  the  head  in  hemicrania,  of  their  natural 
fhare  of  fenforial  power ; and  hence  the  fecondary  parts  of 
thefe  fenlitive  trains  of  aflociation  become  pained  from  the  de- 
ficiency of  their  ufual  motions,  which  is  accompanied  with  de-i 
ficiency  of  fecretions  and  of  heat.  See  Sedl.  IV.  c.  XII.  C, 
3.  XXXIV.  x. 

Why  does  the  pain  of  the  primary  part  of  the  aflociation 
ceafe,  when  that  of  the  feepndary  part  commences  ? This  is  a 
queftion  of  intricacy,  but  perhaps  not  inexplicable.  The  pain 
of  the  primary  part  of  thefe  aflociated  trains  of  motion  was 
owing  to  too  great  ftimulus,  as  of  the  ftone  at  the  neck  of  the 
bladder,  and  was  confequently  caufed  by  too  great  adlion  of 


330  DISEASES  OF  ASSOCIATION.  Sect.  XXXV.  2- 

the  pained  part.  This  greater  aftion  than  natural  of  the  pri- 
mary part  of  thefe  affociated  motions,  by  employing  or  ex- 
pending the  fenforial  power  of  irritation  belonging  to  the  whole 
affociated  train  of  motions,  occafioned  torpor,  and  confequent 
pain,  in  the  fecondary  part  of  the  affociated  train ; which  was 
poffeffed  of  greater  fenfibility  than  the  primary  part  of  it.  Now, 
the  great  pain  of  the  fecondary  part  of  the  train,  as  foon  as  it 
commences,  employs  or  expends  the  fenforial  power  of  fenfa- 
tion belonging  to  the  whole  affociated  train  of  motions ; and 
in  confequence  the  motions  of  the  primary  part,  though  in- 
creafed  by  the  ftimulus  of  an  extraneous  body,  ceafe  to  be  ac- 
companied with  pain  or  fenfation. 

It  this  mode  of  reafoning  be  juft,  it  explains  a curious  fa£t, 
why,  when  two  parts  of  the  body  are  ftrongly  ftimulated,  the 
pain  is  felt  only  in  one  of  them,  though  it  is  poffible,  by  volun- 
tary attention,  it  may  be  alternately  perceived  in  them  both. 
In  the  fame  manner,  when  two  new  ideas  are  prefented  to  us 
from  the  ftimulus  of  external  bodies,  we  attend  to  but  one  of 
them  at  a time.  In  other  words,  when  one  fet  of  fibres,  whether 
of  the  mufcles  or  organs  of  fenfe,  contract  fo  ftrongly  as  to  excite 
much  fenfation,  another  fet  of  fibres,  contracting  more  weaklv, 
do  not  excite  fenfation  at  all,  becaufe  the  fenforial  power  of 
fenfation  is  pre-cccupied  by  the  firft  fet  of  fibres.  So  we  cannot 
will  more  than  one  effedt  at  once,  though,  by  affociations  pre- 
vioufly  formed,  we  can  move  many  fibres  in  combination. 

Thus,  in  the  inftances  above  related,  the  termination  of  the 
bile-dudt  in  the  duodenum,  and  the  exterior  extremity  of  the 
urethra,  are  more  fenftble  than  their  other  terminations. 
When  thefe  parts  are  deprived  of  their  ufual  motions,  bv  defi- 
ciency of  the  fenforial  power  of  irritation,  they  become  pain- 
ful, according  to  law  the  fifth  in  Section  IV.  and  the  lefs  pain 
originally  excited  by  the  ftimulus  of  concreted  bile,  or  of  a 
ftone  at  their  other  extremities  ceafes  to  be  perceived.  After- 
wards, however,  wdren  the  concretions  of  bile,  or  the  ftone 
on  the  urinary  bladder,  become  more  numerous  or  larger,  the 
pain  from  their  increafed  ftimulus  becomes  greater  than  the  af- 
fociated pain  ; and  is  then  felt  at  the  neck  of  the  gall  bladder  or 
urinary  bladder  ; and  the  pain  of  the  glans  penis,  or  at  the  pit 
of  the  ftomach,  ceafes  to  be  perceived. 

2.  Examples  of  the  fecond  mode,  where  the  increafed  aclion 
of  the  primary  part  of  a train  of  fenlitive  affociation  ceafes, 
when  that  of  the  fecondary  part  coYnmences,  are  alio  not  un- 
frequent ; as  this  is  the  ufual  manner  of  the  tranflation  of  in- 
flammations from  internal  to  external  parts  of  the  fyftem,  Inch 
as  when  an  inflammation  of  the  liver  or  ftomach  is  tranflated 

to 


Sect.  XXXV.  2.  DISEASES  OF  ASSOCIATION.  33? 

to  the  membranes  of  the  foot,  and  forms  the  gout ; or  to  the 
Ikin  of  the  face,  and  forms  the  rofy  drop ; or  when  an  inflamma- 
tion of  the  membranes  of  the  kidneys  is  translated  to  the  Ikin 
of  the  loins,  and  forms  one  kind  of  nerpes,  called  fhingles  : in 
thefe  cafes,  by  whatever  caufe  the  original  inflammation  may 
have  been  produced,  as  the  fecondary  part  of  the  train  of  fenll- 
tive  affbciation  is  more  fenfible,  it  becomes  exerted  with  greater 
violence  than  the.firft  part  of  it ; and  by  both  its  increafed  pain, 
and  the  increafed  motion  of  its  fibres,  fo  far  diminilhes  or  ex- 
it aufts  the  fenforial  power  of  fenfation,  that  the  primary  part 
of  the  train  being  lefs  fenfible,  ceafes  both  to  feel  pain  and  to 
afil  with  unnatural  energy. 

3.  Examples  of  the  third  mode,  where  the  primary  part  of  a 
train  of  fentitive  affbciation  of  motions  may  experience  increaf- 
ed fenfation,  anu  the  fecondary  part  increafed  action,  are  like- 
wife  not  unfrequent ; as  it  is  in  this  manner  that  moft  inflamma- 
tions commence.  Thus,  after  ftandingfome  time  in  fnow,  the 
feet  become  affected  with  the  pain'  of  cold,  and  a common  co- 
ryza, or  inflammation  of  the  membrane  of  the  noftrils  fucceeds. 
It  is  probable  that  the  internal  inflammations,  as  pleurifies,  or 
hepatitis,  which  are  produced  after  the  cold  paroxyfm  of  lever., 
originate  in  the  fame  manner  from  the  fympathy  of  thofe  parts 
with  fome  others,  which  were  previoully  pained  from  quie- 
fcence ; as  happens  to  various  parts  of  the  fyffem  during  the  cold 
fits  of  fevers.  In  thefe  cafes  it  would  feern  that  the  fenforial 
power  of  fenfation  becomes  accumulated  during  the  pain  of 
cold,  as  the  torpor  of  the  veffels  occafioned  by  thedefefil  of  heat 
contributes  to  the  increafe  or  accumulation  of  the  fenforial  power 
of  irritation,  and  that  both  thefe  become  exerted  on  fome  inter- 
nal part,  which  was  not  rendered  torpid  by  the  cold  which  af- 
fe filed  the  external  parts,  nor  by  its  affbciation  with  them;  or 
which  fooner  recovered  its  fenfibility. 

4.  An  example  of  the  fourth  mode,  or  where  the  primary 
part  of  a fenfitive  affbciation  of  motions  may  have  increafed 
afifion,  and  the  fecondary  part  increafed  fenfation,  may  be  taken 
from  the  pain  of  the  fhoulder,  which  attends  inflammation  of 
the  membranes  of  the  liver.  See  Hepatitis,  Clafs  IV.  2.1.6.  In 
this  civcumftance  fo  much  fenforial  power  feems  to  be  expended 
in  the  violent  afilions  and  fenfations  of  the  inflamed  membranes 
of  the  liver,  that  the  membranes  affcciated  with  them  become 
quiefcent  to  their  ufual  ftimuli,  and  painful  in  confequence. 

There  may  be  other  modes  in  which  the  primary  and  fecond- 
ary parts  of  the  trains  of  aflociated  fenfitive  motions  may  reci- 
procally affefil  each  other,  as  may  he  feen  by  looking  over  Clafs 
IV.  in  the  Catalogue  of  Difeafes ; all  which  may  probably  be 

X x refolved 


332  PERIODS  OF  DISEASES.  Sect.  XXXVI.  r. 

refolved  into  the  plus  and  minus  of  fenforial  power ; bur  we 
have  not  yet  had  fudicient  observations  made  upon  them  with 
a view  to  this  dodtrine. 

III.  The  affociated  trains  of  our  ideas  may  have  fympathies, 
and  their  primary  and  fecondary  parts  a£Fe£I  each  other  in  fome 
manner  fimilar  to  thofe  above  defcribed ; and  may  thus  occaiion 
various  curious  phenomena  net  yet  adverted  to,  beGdes  thofe 
explained  in  the  fedlions  on  dreams,  reveries,  vertigo,  anddrun- 
kennefs;  and  may  thus  difturb  the  deductions  of  our  reafon- 
ings,  as  well  as  the  ftreams  of  our  imaginations  prefent  us  w ith 
faife  degrees  of  fear,  attach  unfounded  value  to  trivial  civcum- 
ftances,  give  occafion  to  our  early  prejudices  and  antipathies, 
and  thus  embarrafs  the  happinefs  of  our  lives.  A copious  and 
curious  harveft  might  be  reaped  from  this  province  o:  fcience, 
in  which,  however,  I fir  all  not  at  prefent  wield  my  fickle. 


SECT.  XXXVI. 

OF  THE  PERIODS  OF  DISEASES. 

I.  Mufcles  excited  by  volition  foon  ceafe  io  contrail,  or  by 
fenfation , or  by  irritation , owing  to  the  exhauflion  of  fen- 
forial power.  Mufcles  fubjeiied  to  lefs  Jlimulus  have  their 
fenforial  power  accumulated . Hence  the  periods  of  fame 
fevers.  Want  of  irritability  after  intoxication.  11.  i„ 
Natural  allions  catenated  with  daily  habits  of  life.  2. 
With  folar  periods.  Periods  of  flcep.  Of  evacuating  the 
bowels.  3.  Natural  allions  catenated  with  lunar  periods. 
Menfruation.  Venereal  orgafm  of  animals.  Barrenncfs. 
III.  Periods  of  difeafed  animal  ail  ions  from  Jlatcd  returns 
of  noilurnal  cold ; from  folar  and  lunar  infucnce.  Periods 
of  diurnal  fever,  heilic  fever,  quotidian,  tertian,  quartan 
fever.  Periods  of  gout,  plcurify , of  fevers  with  arterial 
debility,  and  with  arterial  frength.  Periods  of  rhapha- 
nia,  of  nervous  cough,  hemicrania , arterial  hamorrhages , 
hamorrhsids,  hcemoptoe,  epilepfy,  palfy,  apoplexy,  mad~ 
nefs.  IV.  Critical  days  depend  on  lunar  periods.  Lunar 
periods  in  the  fnall-pox. 

I.  IF  any  of  our  mufcles  be  made  to  contract  violently  by 
the  power  of  volition,  as  thofe  of  the  fingers,  when  anv  one 
hangs  by  his  hands  on  a Iwing,  fatigue  loon  enfues,  and  the 
mufcles  ceafe  to  a£t,  owing  to  the  temporary  exhauflion  of 
the  fpirit  of  animation:  as  foon  as  this  is  again  accumulated 
in  the  mufcles,  they  are  ready  to  contradf  again  by  the  efforts 
of  volition. 


Thofe 


Sect.  XXXVI.  i.  PERIODS  OF  DISEASES. 


333 

Thofe  violent  mufcular  adlions  induced  by  pain  become,  in 
the  fame  manner,  intermitted  and  recurrent;  as  in  labour-pains, 
vomiting,  tenefmus,  ftrangury;  owing,  hkewife,  to  the  tempo- 
rary exhaullion  of  the  fpirit  of  animation,  as  above  mentioned. 

When  any  ftimulus  continues  long  to  adx  with  unnatural 
violence,  fo  as  to  produce  too  energetic  action  of  any  of  our 
moving  organs,  thofe  motions  foon  ceafe,  though  the  ftimulus 
'Continues  to  adt ; as  in  looking  long  on  a bright  objedl,  as  on 
an  inch-fquare  of  ted  filk  laid  on  white  paper  in  the  funfhine. 
See  Plate  1.  in  Sedt.  III.  i. 

On  the  contrary,  where  lefs  of  the  ftimulus  of  volition,  fen- 
fation,  or  irritation,  has  been  applied  to  a mufcle  than  ufual, 
there  appears  to  be  an  accumulation  of  the  fpirit  of  animation 
in  the  moving  organ,  by  which  it  is  liable  to  at R with  greater 
energy  from  lefs  quantity  of  ftimulus  than  was  previouily  ne- 
ceffary  to  excite  it  into  fo  great  action ; as,  after  having  been 
immerfed  in  l'now,  the  cutaneous  veffels  of  our  hands  are  ex- 
cited into  ftronger  adtion  by  the  ftimulus  of  a lefs  degree  of 
teat  than  would  previouily  have  produced  that  effedl. 

From  hence  the  periods  of  fome  fever-fits  may  take  their  ori- 
gin, either  limply,  or  by  their  accidental  coincidence  with  lunar 
and  folar  periods,  or  with  the  diurnal  periods  of  heat  and  cold  to 
be  treated  of  below;  for,  during  the  cold  fit  at  the  commencement 
.of  a fever,  from  whatever  caufe  thatcold  fit  may  have  been  in- 
duced, it  follows,  i.  That  the  fpirit  of  animation  muft  become 
accumulated  in  the  parts  which  exert,  during  this  cold  fit,  lefs 
■than  their  natural  quantity  of  adlion.  2.  If  the  caufe  produc- 
ing the  cold  fit  does  not  increafe,  or  becomes  diminifhed,  the 
parts  before  benumbed  or  inadlive  become  now  excitable  by 
finaller  ftimulus,  and  are  thence  thrown  into  more  violent  ac- 
tion than  is  natural ; that  is,  a hot  fit  fucceeds  the  cold  one. 
3.  Ey  the  energetic  adfion  of  the  fyftem  during  the  hot  fit,  if 
it  continues  long,  an  exhaullion  of  the  fpirit  of  animation  takes 
place,  and  another  cold  fit  is  liable  to  fucceed,  from  the  mov- 
ing fyftem  not  being  excitable  into  adtion  from  its  ufual  ftimu- 
lus. This  inirritability  of  the  fyftem  from  a too  great  previous 
ftimulus,  and  confequent  exhauftian  of  l'enforial  power,  is  the 
caufe  of  the  general  debility,  and  ficknefs,  and  head-ach,  fome 
hours  after  intoxication.  And  hence  we  fee  one  of  the  caufes 
of  the  periods  of  fever-fits ; which,  however,  are  frequently 
combined  with  the  periods  of  oui  diurnal  habits,  or  of  heat 
and  cold,  or  of  folar  or  lunar  periods. 

When,  befides  the  tendency  to  quiefcence  occafioned  by  the 
•expenditure  of  fenforial  power  during  the  hot  fit  of  fever,  fome 
Other  caufe  of  torpor,  as  the  folar  or  lunar  periods,  is  neceffary 

to 


PERIODS  OF  DISEASES.  Sect.  XXXVI.  2. 


334 

to  the  introduction  of  a fecond  cold  fit,  the  fever  becomes  of 
the  intermittent  kind;  that  is,  there  is  a fpaceot  time  intervenes 
between  the  end  of  the  hot  fit,  and  the  commencement  of  the 
next  cold  one.  But  where  no  exterior  caufe  is  neceffary  to  the 
introduction  of  the  fecond  cold  fit,  no  fuch  interval  of  health  in- 
tervenes ; hut  the  fecond  cold  fit  commences  as  foon  as  the  fen- 
forial  power  is  fufficiently  exhaufted  by  the  hot  fit,  and  the  fever 
becomes  continual. 

II.  1.  Tiie  following  are  natural  animal  actions,  which  are 
frequently  catenated  with  our  daily  habits  of  lire,  as  well  as  ex- 
cited by  their  natural  irritations.  The  periods  of  hunger  and 
thirft  become  catenated  with  certain  portions  of  time,  or  degrees 
of  exhauftion,  or  other  diurnal  habits  of  life.  And  if  the  pain 
of  hunger  be  not  relieved  by  taking  food  at  the  ul'ual  time,  it  is 
liable  to  ceafe  till  the  next  period  of  time  or  other  habits  recur  : 
this  is  not  only  true  in  refpect  to  our  general  deiire  ot  tood, 
but  the  kinds  of  it  alfo  are  governed  by  this  periodical  habit; 
info  much,  that  beer  taken  to  breakfaft  will  difturb  the  digeftion 
of  thofe  who  have  been  accuflomed  to  tea ; and  tea  taken  at  din- 
ner will  difagree  with  thofe  who  have  been  accuflomed  to  beer. 
"Whence  it  happens,  that  thofe  who  have  weak  ltomachs  will 
be  able  to  digeflt  more  food,  if  they  take  their  meals  a:  regular 
hours  ; becaufe  they  have  both  the  ftimulus  of  fine  ah  mem  drey 
take,  and  the  periodical  habit,  to  affift  their  digefuon. 

The  periods  of  emptying  the  bladder  are  not  only  dependent 
en  the  acrimony  or  diftention  of  the  water  in  it,  but  are  fre- 
quently catenated  with  the  external  cold  applied  to  the  fkin,  as 
in  cold  bathing,  or  walking  the  hands;  or  with  other  habits  ot 
life,  as  many  are  accuflomed  to  empty  the  bladder  before  going 
to  bed,  or  into  the  houfe  after  a journey,  and  this  whether  it 
be  full  or  not. 

Our  rimes  of  refpiration  are  notonlv  governed  by  the  ftimu- 
Jus  of  the  blood  in  the  lungs,  or  our  defire  of  frefh  air,  hut  alio 
by  our  attention  to  the  hourly  objects  before  us.  Hence,  when 
a perton  is  earnefllv  contemplating  an  idea  of  grief,  he  forgets 
to  breathe,  till  thefenfation  in  his  lungs  becomes  very  urgent; 
and  then  a iigh  fuccceds  for  the  purpofe  of  more  forcibly  puk- 
ing forwards  the  blood  which  is  accumulated  in  the  lungs. 

Our  times  of  refpiration  are  aifo  f requently  governed  in  part 
by  our  want  ot  a Heady  fupport  for  the  actions  of  our  arms 
and  hands,  as  in  threading  a needle,  or  hewing  wood,  or  in 
fwimming:  when  we  are  intent  upon  thefe  objects,  we  breathe 
at  the  intervals  of  the  exertion  of  the  pecTtoral  mufcles. 

2.  The  foliowing  natural  animal  a (Tons  are  influenced  bv 
folar  periods.  The  periods  of  fleep  and  of  waking  depend 
* muck 


Sect.  XXXVI.  3.  PERIODS  OF  DISEASES.  335 

much  on  the  folar  period ; for  we  are  inclined  to  deep  at  a cer- 
tain hour,  and  to  awake  at  a certain  hour,  whether  we  have 
had  more  or  lefs  fatigue  during  the  day,  if  within  certain  li- 
mits ; and  are  liable  to  wake  at  a certain  hour,  whether  we 
went  to  bed  earlier  or  later  within  certain  limits.  Hence  it  ap- 
pears, that  thofe  who  complain  of  want  of  deep,  will  be  liable 
to  deep  better  or -longer,  if  they  accuflom  themfelves  to  go  to 
red;  and  to  rife  at  certain  hours. 

The  periods  of  evacuating  the  bowels  are  generally  connect  - 
ed  with  fome  part  of  the  folar  day,  as  well  as  with  the  acri- 
mony or  didention  occafioned  by  the  faeces.  Hence,  one  me- 
thod of  corredling  coftivenefs  is  by  endeavouring  to  edablifli  a 
habit  of  evacuation  at  a certain  hour  of  the  day,  as  recommended 
by  Mr.  Locke,  which  may  be  accomplithed  by  udng  daily 
voluntary  efforts  at  thofe  times,  joined  with  the  ufual  ftimulus 
of  the  material  to  be  evacuated. 

3.  The  following  natural  animal  adtions  are  connected  with 
lunar  periods.  1.  The  periods  of  female  menftruation  are 
connected  with  lunar  periods  to  great  exaTnefs,  in  fome  in- 
ilances  even  to  a few  hours.  Thefe  do  not  commence  or  ter- 
minate at  the  full  or  change,  or  at  any  other  particular  part  of 
the  lunation ; but  after  they  have  commenced  at  any  part  of  it, 
they  continue  to  recur  at  that  part  with  great  regularity,  unlefs 
difturbed  by  fome  violent  circumftance,  as  explained  in  Sedition 
XXXII.  No.  6.  Their  return  is  immediately  caufed  by  defi- 
cient venous  abforption,  which  is  owing  to  the  want  of  the  fti- 
mulus, defigned  by  nature,  of  amatorial  copulation,  or  of  the 
growing  foetus.  When  the  catamenia  returns  fooner  than  the 
period  of  lunation,  it  thews  a tendency  of  the  conflitution  to 
inirritability ; that  is,  to  debility,  or  deficiency  of  fenforial  power, 
and  is  to  be  relieved  by  fmall  dofes  of  fteel  and  opium. 

The  venereal  orgafm  of  birds  and  quadrupeds  feems  to  com- 
mence or  return  about  the  moft  powerful  lunations  at  the  vernal 
or  autumnal  equinoxes ; but  if  it  be  difappointed  of  its  objedt, 
it  is  faid  to  recur  at  monthly  periods ; in  this  refpedt  refembling 
the  female  catamenia.  Whence  it  is  believed,  that  women  are 
more  liable  to  become  pregnant  at  or  about  the  time  of  their 
catamenia,  than  at  the  intermediate  times ; and  on  this  account 
they'-  are  feldom  much  miftaken  in  their  reckoning  of  nine  lunar 
periods  from  the  lafc  menftruation:  the  inattention  to  this  may 
fometimes  have  been  the  caufe  of  fuppofed  barrennefs,  and  is 
therefore  worth  the  obfervation  of  thofe  who  with  to  have 
children. 

III.  We  now  come  to  the  periods  of  difeafea  animal  acftions. 
The  periods  of  fever-fits,  which  depend  on  the  ftated  returns 

of 


336  PERIODS  OF  DISEASES.  Sect.  XXXVI.  3. 

of  nodturnal  cold,  are  di  feu  fled  in  Sedl.  XXXII.  3.  Thofe 
which  originate  or  recur  at  folar  or  lunar  periods,  are  alfo  ex- 
plained in  Sedtion  XXXII.  6.  Thefe  we  fhall  here  enume- 
rate ; obferving,  however,  that  it  is  not  more  furprizing.  rl. at 
the  influence  of  the  varving  attradtions  of  the  fun  an<l  moon 
fhould  raife  the  ocean  into  mountains,  than  that  it  fhould  af- 
fedt  the  nice  fenfihilities  of  animal  bodies;  though  the  manner 
of  its  operation  on  them  is  difficult  to  be  underflood.  It  is 
probable,  however,  that  as  this  influence  gradually  leflens  dur- 
ing the  courfe  of  the  day,  or  of  the  lunation,  or  of  the  t ear, 
fome  adtions  of  our  fyflem  become  lefs  and  lefs,  tiil  at  length 
a total  quiefcer.ee  of  fome  part  is  induced ; which  is  tire  com- 
mencement of  the  paroxyfms  of  fever,  of  menftruauon,  of 
pain,  with  decreased  action  of  the  affedted  organ,  and  of  con- 
fequent  convulfion. 

1.  A diurnal  fever,  in  fome  weak  people,  is  diftindllv  cb- 
ferved  to  come  on  towards  evening,  and  to  ceafe  with  a moift 
fkin  early  in  the  morning,  obeying  the  folar  periods,  Pcrfons 
of  weak  conftitutions  are  liable  to  get  into  better  fpirirs  at  the 
accefs  of  the  hot  flt  of  this  evening  fever,  and  are  thence  in- 
clined to  flt  up  late,  which,  by  further  enfeebiing  them,  increafes 
the  difeafe ; whence  they  lofe  their  ftrength  and  their  colour. 

2.  The  periods  of  hedtic  fever,  fuppofed  to  ariie  from  ab- 
forption  of  matter,  obey  the  diurnal  periods  like  the  above, 
having  the  exacerbefcence  towards  evening,  and  its  rcraiflion 
early  in  the,  morning,  with  fweats,  or  diarrhoea,  or  urine  with 
white  fedimeut. 

The  periods  of  quotidian  fever  are  either  catenated  with  fo- 
lar time,  and  return  at  the  intervals  of  twenty-four  hours,  or 
with  lunar  time,  recurring  at  the  intervals  of  about  twenty-five 
hours.  There  is  great  ufe  in  knowing  with  what circumftances 
the  periodical  return  of  new  morbid  motions  are  conjoined,  as 
the  moft  effectual  times  of  exhibiting  the  proper  medicines  are 
thus  determined.  So,  if  the  torpor  which  ufhers  in  an  ague 
fit  is  catenated  with  the  lunar  day,  it  is  known  when  the  hark 
or  opium  nnift  be  given,  fo  as  to  exert  its  principal  effect  about 
the  time  of  the  expedted  return.  Solid  opium  fhould  be  given 
about  an  hour  before  the  expedted  cold  fit;  liquid  opium  and 
wine  about  half  an  hour;  the  bark  repeatedly  for  fix  or  eight 
hours  previous  to  the  expedted  return. 

4.  The  periods  of  tertian  fevers,  reckoned  from  the  com- 
mencement of  one  cold  fit  to  the  commencement  of  the  next 
cold  fit,  recur,  with  folar  intervals  of  forty -eight  hours,  or  with 
lunar  ones  of  about  fifty  hours.  When  thefe  t:mes  of  recur- 
rence begin  one  or  two  i tours  earlier  than  the  folar  periods,  it 

fhews, 


Sect.  XXXVI.  3.  PERIODS  OF  DISEASES.  337 

fhews,  that  the  torpor  or  cold  lit  is  produced  hy  lefs  external 
influence;  and,  therefore,  that  it  is  more  liable  to  degenerate 
into  a fever  with  only  remiffions : fo,  when  mcnftruation  recurs 
fooner  than  the  period  of  lunation,  it  fhews  a tendency  of  the 
habit  to  torpor  or  inirritability. 

5.  The  periods  of  quartan  fevers  return  at  folar  intervals  of 
feventy-two  hours,  or  at  lunar  ones  of  about  feventy-four  hours 
and  an  half.  This  kind  of  ague  appears  mod  in  tnoift  cold  au- 
tumns, and  in  cold  countries  replete  with  marfhes.  It  is  at- 
tended with  greater  debility,  and  its  cold  accefs  more  difficult 
to  prevent.  For,  where  there  is  previously  a deficiency  of  fenfo- 
rial  power,  the  conftitution  is  liable  to  run  into  greater  torpor 
from  arjy  further  diminution  of  it:  two  ounces  of  bark  arid 
fome  fteel  fhould  be  given  on  the  day  before  the  return  of  the 
cold  paroxyfm,  and  a pint  of  wine,  by  degrees,  a few  hours  be- 
fore its  return,  and  thirty  drops  of  laudanum  one  hour  before 
the  expected  cold  fit. 

6.  The  periods  of  the  gout  generally  commence  about  an 
hour  before  fun-rife,  which  is  ufually  the  coldeld  part  of  the 
twenty-four  hours.  The  greater  periods  of  the  gout  feem  alfo 
to  obferve  the  folar  influence,  returning  about  the  fame  feafon 
of  the  year. 

7.  The  periods  of  the  pleurify  recur  with  exacerbation  of  the 
pain  and  fever  about  fun-fet,  at  which  time  venefeclion  is  of  molt 
fervice.  The  fame  may  be  obferved  of  the  inflammatory  rheu- 
matil'm,  and  other  fevers  with  arterial  ftrength,  which  feem  to 
obey  folar  periods ; and  thofe  with  debility  feem  to  obey  lunar 
ones.  . 

8.  The  periods  of  fevers  with  arterial  debility  feem  to  obey  the 
lunar  day,  having  their  accefs  daily  nearly  an  hour  later;  and 
have  fometimes  two  accedes  in  a day,  refembling  the  lunar  ef- 
fects upon  the  tides. 

9.  The  periods  of  rhaphania,  or  convulfions  of  the  limbs 
from  rheumatic  pains,  feem  to  be  connected  with  folar  influ- 
ence, returning  at  nearly  the  fame  hour  for  weeks  together,  un- 
lefs  difturbed  by  the  exhibition  of  powerful  dofes  of  opium. 

So  the  periods  of  Tuffis  ferina,  or  violent  cough  with  flow 
pulfe,  called  nervous  cough,  recurs  by  folar  periods.  Five 
grains  of  opium,  given  at  the  time  the  cough  commenced,  dif- 
turbed the  period,  from  feven  in  the  evening  to  eleven,  at  which, 
time  it  regularly  returned  for  fome  days,  during  which  time  the 
opium  was  gradually  omitted.  Then  120  drops  of  laudanum 
were  given  an  hour  before  the  accefs  of  the  cough,  and  it  totally 
ceafed.  The  laudanum  was  continued  a fortnight,  and  then 
gradually  difeontinued. 


IO.  The 


338  PERIODS  OF  DISEASES.  Sect.  XXXVI. 

10.  The  periods  of  heraicrania,  and  of  painful  epilepfv,  are 
liable  to  obey  lunar  periods,  both  in  their  diurnal  returns,  and  in 
then-  greater  periods  of  weeks;  but  are  alfo  induced  by  odier  ex- 
citing caufes. 

11.  The  periods  of  arterial  haemorrhages  feem  to  return  a: 
folar  periods,  about  the  fame  hour  of  the  evening  or  morning. 
Perhaps  the  venous  haemorrhages  obey  the  lunar  periods,  as  the 
catamenia  and  haemorrhoids. 

12.  Tiie  periods  of  the  haemorrhoids,  or  piles,  infome,  re- 
cur monthly,  in  others  only  at  the  greater  lunar  influence 
about  the  equinoxes. 

13.  I he  periods  of  haemoptoe  fometimes  obey  folar  influ- 
ence, recurring  early  in  the  morning  for  feveral  days ; and 
fometimes  lunar  periods,  recurring  monthly ; and  fometimes 
depend  on  our  hours  of  fleep.  See  Ciafs  I.  2.  1.  9. 

14.  Many  of  the  firft  periods  of  epileptic  flrs  obey  the 
monthly  lunation  with  fome  degree  of  accuracy  ; others  recur 
only  at  the  moft  powerful  lunations  before  the  vernal  equinox, 
and  after  die  autumnal  one ; but  when  the  conftitution  has 
gained  a habit  of  relieving  difagreeable  fenfations  by  this  kind 
of  exertion,  the  fit  recurs  from  any  flight  caufe. 

15.  The  attack  of  palfy  and  apoplexy  is  known  to  recur 
with  great  frequency  about  the  equinoxes. 

16.  There  are  numerous  inftances  of  the  effedl  of  the  luna- 
tions upon  the  periods  of  infanitv  ; whence  the  name  of  lunatic 
has  been  given  to  thofe  afflicfted  with  this  difeafe. 

IV.  The  critical  days,  in  which  fevers  are  fuppofed  to  ter- 
minate, have  employed  the  attention  ot  medical  philofophers 
from  the  days  of  Hippocrates  to  the  prefent  time.  In  whatever 
part  of  a lunation  a fever  commences,  which  owes  either  its 
whole  caufe  to  folar  and  lunar  influence,  or  to  this  in  con- 
junction with  other  caufes,  it  would  feem,  that  the  effect 
would  be  the  greateft  at  the  full  and  new  moon,  as  the  tides 
rife  higheft  at  thofe  times,  and  would  be  the  leal!  at  the  quad- 
ratures: thus,  if  a fever-fit  fhould  commence  at  the  new  or 
lull  moon,  occafioned  by  the  folar  and  lunar  attraction,  dimi- 
l! filling  fome  chemical  affinity  of  the  particles  ot  blocd,  and 
thence  decreafing  their  ftimulus  on  our  fanguiferous  fyftem,  as 
mentioned  in  Sect.  XXXII.  6.  this  efl'eCt  will  daily  decreals 
for  the  fiift  feven  days,  and  will  then  iilcreale  till  about  the 
fourteenth  day,  and  will  again  decreafe  till  about  the  twenty - 
firil  day,  and  increafe  again  till  the  end  of  the  lunation.  It  a 
fever-fit  from  the  above  caufe  fhould  commence  on  the  feven ch 
day  after  either  lunation,  the  reverie  of  the  above  circumftances 
would  happen.  Now,  it  is  probable,  that  thofe  fevers,  w hole 

crifis 


Sect.  XXXVII.  i.  DIGESTION,  &c,  339 

crifis  or  terminations  are  influenced  by  lunations,  may  begin  at 
one  or  other  of  the  above  times,  namely,  at  the  changes  or 
quadratures  ; though  fufficient  obfervations  have  not  been, 
made  to  afcertain  this  circumftance.  Hence  I conclude,  that 
the  fmall-pox  and  meafles  have  their  critical  days,  not  go- 
verned by  the  times  required  for  certain  chemical  changes  in 
the  blood,  which  affedf  or  alter  the  ftimulus  of  the  contagious 
matter,  but  from  the  daily  increafing  or  decreaflng  effect  of 
this  lunar  link  of  catenation,  as  explained  in  Section  XVII. 
3.  3.  And  as  other  fevers  terminate  moff  frequently  about  the 
feventh,  fourteenth,  twenty-fuft,  or  about  the  end  of  four 
weeks,  when  no  medical  afliftance  has  difturbed  their  periods, 
I conclude,  that  thefe  crifes,  or  terminations,  are  governed  by 
periods  of  the  lunations,  though  we  are  ftill  ignorant  of  their 
manner  of  operation. 

In  the  diftindt  tmall-pox,  the  veftiges  of  lunation  are  very 
apparent:  after  inoculation,  a quarter  of  a lunation  precedes 
the  commencement  of  the  fever,  another  quarter  terminates 
with  the  complete  eruption,  another  quarter  with  the  com- 
plete maturation,  and  another  quarter  terminates  the  complete 
abforption  of  a material  now  rendered  inoffenfive  to  the  con- 
ftitution. 


SECT.  XXXVII. 

OF  DIGESTION,  SECRETION,  NUTRITION. 

I.  Cryjials  incr'eafe  by  the  greater  attraction  of  their  fides. 
Accretion  by  chemical  precipitations , by  welding , by  pref- 
Jure,  by  agglutination.  II.  Hunger , digefiion ; why  it 
cannot  be  imitated  cut  of  the  body.  LaCtcals  abforb  by 
animal  feledion , or  appotency.  III.  The  glands  and  pores 
abforb  nutritious  particles  by  animal  f election.  Organic 
particles  of  Buff  on.  Nutrition  applied  at  the  time  of  elon- 
gation of  fibres.  Like  inflammation.  IV.  It  feems  eafier 
to  have  preferved  animals  than  to  re-produce  them.  Old 
age  and  death  from  inirritability.  Three  caufcs  of  this. 
Original  fibres  of  the  organs  of  fenfe  and  mufcles  un- 
changed. V.  Art  of  producing  long  life. 

I.  THE  larger  cryftals  of  faline  bodies  may  be  conceived 
to  arife  from  the  combination  of  fmaller  cryftals  of  the  fame 
form,  owing  to  the  greater  attradfions  of  their  lides  than  of 
their  angles.  Thus,  if  four  cubes  were  floating  in  a fluid, 
whofe  fridtion  or  refiftance  is  nothing,  it  is  certain  the  Tides  of 

Y y thefe 


3^0  DIGESTION,  Sec.  Sect.  XXXVII. 2. 

thefe  cubes  would  attradl  each  other  Rronger  than  their  angles  : 
and  hence  that  thefe  four  fmafler  cubes  vrould  lb  arrange  them- 
lelves  as  to  produce  one  larger  one. 

There  are  other  means  of  chemical  accretion,  fuch  as  tire 
depufitions  of  diffolved  calcareous  or  fiiiceous  particles,  as  are 
leen  in  the  formation  ol  the  flaladbites  ot  limeftone  in  Derby- 
fhire,  or  ofcalcedone  in  Cornwall.  Other  means  of  adhc-lion 
are  produced  by  heat  and  preffure,  as  in  the  welding  of  iron- 
bars ; and  other  means,  by  fimple  preffure,  as  in  forging  two 
pieces  of  caeutchou,  or  elaftic  gum,  to  adhere;  and,  laftiv,  by 
the  agglutination  of  a third  fubibance  penetrating  the  pores  of 
the  other  two,  as  in  the  agglutination  of  wood  by  means  of 
animal  gluten.  Though  the  ultimate  particles  of  animal  bo- 
dies are  held  together  during  life,  as  well  as  after  death,  by  their 
fpecific  attraction  of  coheilon,  like  all  other  matter;  yet  it  th.es 
not  appear,  that  their  original  organization  was  produced  by 
chemical  laws ; and  their  produdbion  and  increafe  muff  there- 
fore only  be  looked  for  from  the  laws  of  animation. 

II.  When  the  pain  of  hunger  requires  relief,  certain  parts 
of  the  material  world  which  lurround  us,  when  applied  to  our 
palates,  excite  into  action  the  tnufcles  of  deglutition,  and  the 
material  is  fwallowed  into  the  ftomach.  Here  the  new  aliment 
becomes  mixed  with  certain  animal  fluids,  and  undergoes  a che- 
mical procefs,  termed  digeftion ; which,  however,  chemiltry 
has  not  yet  learnt  to  imitate  out  of  the  bodies  of  livingranimals 
or  vegetables.  This  procefs  feems  very  fimilar  to  the  faccha- 
rine  procefs  in  the  lobes  of  farinaceous  feeds,  as  of  barley,  when 
it  begins  to  germinate;  except  that,  along  with  the  iugar,  oil 
and  mucilage  are  alio  produced;  which  ■form  the  chyle  ot  ani- 
mals, which  is  very  fimilar  to  their  milk. 

The  reafon,  1 imagine,  why  this  chyle-making,  or  faccbarine 
procefs,  has  not  yet  been  imitated  by  chemical  operations,  is 
owing  to  the  materials  being  in  fuch  a lituation,  in  refpcdb  to 
warmth,  moifture  and  motion,  that  they  will  immediately 
change  into  the  vinous  or  acetous  fermentation,  except  the  new 
fugar  be  ablorbed  by  the  numerous  lacteal  or  lymphatic  veffels, 
as  loon  as  it  is  produced,  which  is  not  eafy  to  imitate  in  the 
laboratory. 

Thefe  iadteal  veffels  have  mouths,  which  are  irritated  into 
adtion  by  the  ltimulus  of  the  fluid -which  furrounds  them;  and 
by  animal  feledtion,  or  appetency,  they  abforb  luch  pan  or  the 
fluid  as  is  agreeable  to  their  palate ; thofe  parts,  for  inftance, 
which  are  already  converted  into  chvle,  before  they  have  time 
to  undergo  another  change  by  a vinous  or  acetous  fermenta- 
tion. This  animal  abforption  of  fluid  is  almoll  vilibleto  the 

uaked 


Sect.  XXXVII.  3.  DIGESTION,  &c.  341 

naked  eye  in  the  adlion  of  the  punfta  lacrymalia,  which  im- 
bibe the  tears  from  the  eye,  and  difcharge  them  again  into  the 
noftrils. 

III.  The  arteries  conftitute  another  refervoir  of  a change- 
ful fluid;  from  which,  after  its  recent  oxygenation  in  the  lungs, 
a further. animal  feledtion  of  various  fluids  is  abforbed  by  the 
numerous  glands : t’nefe  felect  their  relpedrive  fluids  from  the 
blood,  which  is  perpetually  undergoing  a chemical  change: 
but  the  fele£tion  by  thefe  glands,  like  that  of  the  ladleals,  which 
open  their  mouths  into  the  digefting  aliment  in  the  ftomach,  is 
from  aniinal  appetency,  not  from  chemical  affinity;  fecretion 
cannot,  therefore,  be  imitated  in  the  laboratory,  as  it  coniifts 
in  a fele&ion  of  part  of  a fluid  during  the  chemical  change  of 
that  fluid. 

The  mouths  of  the  ladleals  and  lymphatics,  and  the  ulti- 
mate terminations  of  the  glands,  are  finer  than  can  eaflly  be 
conceived;  yet,  it  is  probable  that  the  pores,  or  interftices  of 
the  parts,  or  coats,  which  conftitute  thefe  ultimate  vefifels,  may 
ftill  have  greater  tenuity  ; and  that  thefe  pores,  from  the  above 
analogy,  muft  poflefs  a flmilar  power  of  irritability,  and  ab- 
sorb, by  their  living  energy,  the  particles  of  fluid  adapted  to 
their  purpofes,  whether  to  replace  the  parts  abraded  or  difiolv- 
ed,  or  to  elongate  and  enlarge  themfelves.  Not  only  every 
kind  of  gland  is  thus  endued  with  its  peculiar  appetency,  and 
feledls  the  material  agreeable  to  its  taflce  from  the  blood,  but 
.every  individual  pore  acquires,  by  animal  feledfion,  the  mate.- 
rial  which  it  wants ; and  thus  nutrition  feems  to  be  performed 
in  a manner  fo  flmilar  to  fecretion,  that  they  only  differ  in  the 
one  retaining,  and  the  other  parting  again  with, the  particles 
which  they  have  felecfed  from  the  blood. 

This  way  of  accounting  for  nutrition  from  ftimulus,  and 
the  confequent  animal  feledlion  of  particles,  is  much  more  ana- 
logous to  other  phenomena  of  the  animal  microcofm,  than  by 
having  recourfe  to  the  microlcopic  animalcula,  or  organic  par- 
ticles of  Buffon  and  Needham  ; which,  being  already  com- 
pounded, muff  themfelves  require  nutritive  particles  to  conti- 
nue their  own  exiftence;  and  muft  be  liable  to  undergo  a 
change  by  our  digeftive  or  fecretorv  organs  ; otherwife  mankind 
would  foon  referable,  by  their  theory,  the  animals  which  they 
feed  upon.  He,  who  is  nourifhed  by  beef  or  venifon,  would 
in  time  become  horned ; and  he,  who  feeds  on  pork  or  bacon, 
would  gain  a nofe  proper. for  rooting  into  the  earth,  as  well  as 
for  the  perception  of  odours. 

The  whole  animal  fyftem  may  be  confldered  as  confifting 
of  the  extremities  of  the  nerves,  or  of  having  been  produced  from 

them ; 


342  DIGESTION,  &c.  Sect.  XXXVII.  3. 

them  ; if  we  except  perhaps  the  medullary  part  of  the  brain  re- 
fuling  in  the  head  and  fpine,  and  in  the  trunks  of  the  nerves. 
Thefe  extremities  of  the  nerves  are  either  of  thofe  of  locomotion, 
which  are  termed  mufcular  fibres ; or  of  thofe  of  fenfation, 
which  conftitute  the  immediate  organs  of  fenfe,  and  which  have 
alfo  their  peculiar  motions.  Now,  as  the  fibres  which  con- 
ftitute the  bones  and  membranes,  poffeffed  originally  fenfation 
and  motion,  and  are  liable  again  to  poffefs  them,  when  they 
become  inflamed ; it  follows,  that  thofe  were,  when  firft  formed, 
appendages  to  the  nerves  of  fenfation  or  locomotion,  or  were 
formed  from  them : and  that  hence,  all  thefe  folid  parts  of  the 
body,  as  they  have  orginally  conflfted  of  extremities  of  nerves, 
require  an  appofltion  of  nutritive  particles  of  a fimilar  kind, 
contrary  to  the  opinion  of  BufFon  and  Needham  above  recited. 

Laftly,  as  all  thefe  filaments  have  poffeffed  or  do  poffefs  the 
power  of  contraction,  and  of.confeauent  inertion  or  elongation, 
it  feems  probable  that  the  nutritive  particles  are  applied  during 
their  times  of  elongation,  when  their  original  conftituent  par- 
ticles are  removed  to  a greater  diftance  from  each  other.  For 
each  mufcular  or  fenfual  fibre  may  be  conlidered  as  a row  or 
firing  of  beads,  which  approach  when  in  contraction,  and  recede 
during  its  reft  or  elongation  ; and  our  daily  experience  (hews 
us,  that  great  action  emaciates  the  fyflem,  and  that  it  is  repaired 
during  reft. 

Something  like  dais  is  feen  out  of  the  body  ; for  if  a hair,  or 
a Angle  untwifted  fibre  of  flax  or  filk,  be  foaked  in  w-ater,  it 
becomes  longer  and  thicker  by  the  water  which  is  abforbed  into 
its  pores.  Now,  if  a hair  could  be  fuppofed  to  be  thus  im- 
merfed  in  a folution  of  particles  fimilar  to  thofe  which  compofe 
it,  one  may  imagine  that  it  might  be  thus  increafed  in  weight 
and  magnitude;  as  the  particles  of  oak-bark  increafe  the  fub- 
ftance  of  the  hides  of  beaits  in  the  procefs  of  making  leather.  I 
mention  thefe  not  as  philofophic  analogies,  but  as  fimilies  to  fa- 
cilitate our  ideas,  how  an  accretion  of  parts  may  be  etfedtcd  by 
animal  appetences,  or  feledtions,  in  a manner  fomewhat  fimilar 
to  mechanical  or  chemical  attractions. 

If  thofe  new  particles  of  matter,  previoufly  prepared  by  di- 
g'eftion  and  fanguification,  only  fupply  the  places  of  thofe  which 
have  been  abraded  by  the  adtions  of  the  fyltem,  it  is  properly 
termed  nutrition.  If  they  are  applied  to  the  extremities  of  die 
nervous  fibrils,  or  in  fuch  quantity  as  to  increafe  the  length  or 
craflitude  of  them,  the  body  becomes  at  the  fame  time  enlarged, 
and  its  growth  is  increafed,  as  well  as  its  deficiencies  repaired. 

In  this  laft  cafe  fomething  more  than  a Ample  appofltion  or 
felection  of  particles  feems  to  be  neceffary ; as  many  parts  ot 

the 


Sect.  XXXVII.  4.  DIGESTION,  &c.  343 

the  fyftem,  during  its  growth,  are  caufed  to  recede  from  thofe 
with  which  they  were  before  in  contact;  as  the  ends  of  die 
bones,  or  cartilages,  recede  from  each  other  as  their  growth  ad- 
vances : this  procefs  refembles  inflammation,  as  appears  in  oph- 
thalmy,  or  in  the  production  of  new  flefli  in  ulcers,  where  old 
veflels  are  enlarged  and  new  ones  produced ; and,  like  that,  is 
attended  with  fenfation.  In  this  fituation  the  veflels  become 
diftended  with  blood,  and  acquire  greater  fenfibiiity,  and  may 
thus  be  compared  to  the  erection  of  the  penis,  or  ot  the  nipples 
of  the  breads  of  women  ; while  new  particles  become  added  at 
the  fame  time,  as  in  the  procefs  of  nutrition  above  defcribed. 

When  only  the  natural  growth  of  the  various  parts  of  the 
body  is  produced,  a pleafureable  fenfation  attends  it,  as  in  youth, 
and  perhaps  in  thofe  who  are  in  the  progrefs  of  becoming  fat. 
When  an  unnatural  growth  is  the  confequence,  as  in  inflam- 
matory difeafes,  a painful  fenfation  attends  the  enlargement  of 
the  fyftem. 

IV.  This  appofition  of  new  parts,  as  the  old  ones  difappear, 
felected  from  the  aliment  we  take,  firft  enlarges  and  ftrengthens 
our  bodies  for  twenty  years,  for  another  twenty  years  it  keeps 
us  in  health  and  vigour,  and  adds  ftrength  and  folidity  to  the 
fyftem,  and  then  gradually  ceafes  to  nourifh  us  properly,  and 
for  another  twenty  years  we  gradually  fink  into  decay,  and 
finally  ceafe  to  act  and  to  exift. 

On  confidering  this  fubject,  one  fhoukl  have  imagined,  at 
firft  view,  that  it  might  have  been  eafier  for  nature  to  have  fup- 
ported  her  progeny  for  ever  in  health  and  life,  than  to  have 
perpetually  re-produced  them  by  the  wonderful  and  myfterious 
procefs  of  generation.  But  it  feems  our  bodies,  by  long  habit, 
ceafe  to  obey  the  ftimulus  of  the  aliment  which  fhould  fupport 
us.  After  we  have  acquired  our  height  and  foliditv,  we  make 
no  more  new  parts,  and  the  fyftem  obeys  the  irritations,  fen- 
fations,  volitions,  and  afiociations,  with  lefs  and  lefs  energy,  till 
the  whole  finks  into  inaction. 

Three  caufes  may  confpire  to  render  our  nerves  lefs  excitable, 
which  have  been  already  mentioned.  1.  If  a ftimulus  be  gi  eater 
than  natural,  it  produces  too  great  an  exertion  of  the  ftimulated 
organ,  and,  in  confequence,  exhaufts  the  fpirit  of  animation ; 
and  the  moving  organ  ceafes  to  act,  even  though  the  ftimulus 
be  continued.  And  though  reft  will  recruit  this  exhauftion, 
yet  fotne  degree  of  permanent  injury  remains,  as  is  evident  after 
expofing  the  eyes  long  to  too  ftrong  a light.  2.  If  excitations 
weaker  than  natural  be  applied,  fo  as  not  to  excite  the  organ 
into  action,  (as  when  fmall  doles  of  aloe  or  rhubarb  are  ex- 
hibited) they  may  be  gradually  increafed,  without  exciting  the 

organ 


344  DIGESTION,  &c.  Sect.  XXXVII.  5. 

■organ  into  adlion,  which  will  thus  acquire  a habit  of  difobe- 
dience  to  the  ftimulus:  thus,  by  increafing  the  dole  by  degrees, 
great  quantities  of  opium  or  wine  may  be'taken  without  in- 
toxication. See  Se£t.  XU.  3.  1. 

3.  Another  mode,  by  which  life  is  gradually  undermined,  is 
when  irritative  motions  continue  to  be  produced  in  confequence 
of  ftimulus,  but  are  notiucceeded  by  fenfation:  hence  the  fti- 
mulus  of  contagious  matter  is  not  capable  of  producing  fever 
a fecond  time,  becaufe  it  is  not  fucceeded  by  fenfation.  See 
Se£t.  XII.  3.  6.  And  hence,  owing  to  the  want  of  the  general 
pleafureable  fenfation  which  ought  to  attend  digeftion  and  glan- 
dular fecretion,  an  irkfomenefs  of  life  enfues;  and,  where  this 
is  in  greater  excels,  the  melancholy  ot  old  age  occurs,  with 
torpor  or  debility. 

From  hence  I conclude,  that  it  is  probable  that  the  fibrillas, 
or  moving  filaments  at  the  extremities  of  the  nerves  of  lenfe, 
and  the  fibres  which  conflitute  the  mufcles  (which  are,  perhaps, 
the  only  parts  ol  the  fyftem  that  are  endued  with  contractile 
life)  are  not  changed;  as  we  advance' in  years,  like  the  odier 
parts  of  the  body,  but  only  erdarged  or  elongated  with  our 
growth ; and,  in  confequence,  they  become  lefs  and  Id's  excit- 
able into  adtion.  Whence,  inftead  of  gradually  changing  the 
old  animal,  the  generation  of  a totally  new  one  becomes  necef- 
fary,  with  undiminifhed  excitability;  which  many  years  will 
continue  to  acquire  new  parts,  or  new  foliuity,  and  then,  lofmg 
its  excitability  in  time,  perilh  like  its  parent. 

V.  From  this  idea  the  art  ot  preferving  long  health  and  life 
may  be  deduced,  which  mull:  conlift  in  uiing  no  greater  ftimur 
lus,  whether  of  the  quantity  or  kind  ot  our  food  and  drink,  or 
of  external  circumftances,  luch  as  heat,  and  exercife.  and  wake- 
fulnefs,  than  is  fufficient  to  preferve  us  in  vigour ; and  gradual!’., 
as  we  grow  old,  to  increafe  the  ftimulus  of  our  aliment,  as  die 
anirritsbiiity  of  our  fyftem  increafes. 

The  debilitating  effects  aferibed,  by  the  poet  Martial,  to 
the  exceflive  ufe  of  warm  bathing  in  Italv,  may,  with  equal 
propriety,  be  applied  ro  the  warm  rooms  of  England,  which, 
with  the  general  exceflive  ftimulus  ot  ipii  ituous  or  fermented 
liquors,  and,  in  forne  inftances,  of  immoderate  veuerv,  contri- 
bute to  fhorten  our  lives. 

Balnea , vina,  venus,  corrumpunt  corpora  nostra , 

At  faciunt  viiam  balnea , vina , -cams  ! 

Wine,  women,  warmth,  against  our  lives  combine; 

But  what  is  life  without  warmth,  women,  wine! 


.SECT. 


Sect.  XXXVIII.  i.  OXYGENATION,  &c. 


SECT.  XXXVIII. 

OF  THE  OXYGENATION  OF  THE  BLOOD  IN  THE 
LUNGS,  AND  IN  THE  PLACENTA, 

I.  Blood  abforbs  oxygcne  from  ike  air , whence  phofphoric 
acid , changes  its  colour,  gives  out  heat,  and  fame  phlogiftic 
material,  and  acquires  an  ctherial  J'pirit,  which  is  dijji - 
pated  in  fibrous  motion.  II.  The  placenta  is  a pulmonary 
organ- like  the  gills  of  fifii.  Oxygenation  of  the  blood  from 
air,  from  water,  by  lungs , by  gills,  by  the  placenta  ; necef- 
fity  of  this  oxygenation  to  quadrupeds,  to  fifh , to  the  foetus 
in  utero.  Placental  vcjfiels  infer  ted  into  the  arteries  of  the 
mother.  Ufe  of  cotyledons  in  cows.  JVhy  quadrupeds 
have  not  fanguiferous  lochia.  Oxygenation  of  the  chick 
in  the  egg,  ofjeeds.  III.  The  liquor  amnii  is  not  excre - 
mentilious.  It  is  nutritious.  It  is  found,  in  the  cefophagus 
and  Jlomach,  and  forms  the  meconium.  M-onftrous  births 
without  heads.  Queflion  of  Dr.  Hervey. 

I.  FROM  the  recent  difeoveries  of  many  ingenious  philofo- 
phers  it  appears,  that  during  refpiration  the  blood  imbibes  the 
vital  part  of  the  air,  called  oxygene,  through  the  membranes  of 
the  lungs  ; and  that  hence  refpiration  may  be  aptly  compared 
to  a flow  eombuftion.  As  in  combuftion  the  oxygene  of  the 
atmofphere  unites  with  Tome  phlogiftic  or  inflammable  body, 
and  forms  an  acid  (as  in  the  production  of  vitriolic  acid  from 
fulphur,  or  carbonic  acid  from  charcoal,)  giving  out  at  the 
fame  time  a quantity  of  the  matter  of  heat ; fo  in  refpiration  the 
oxygene  of  the  air  unites  with  the  phlogiftic  part  of  the  blood, 
and  probably  produces  phofphoric  or  animal  acid,  changing 
tire  colour  of  the  blood  from  a dark  to  a bright  red ; and  proba- 
bly fome  of  the  matter  of  heat  is,  at  the  fame  time,  given  out, 
according  to  the  theory  of  Dr.  Crawford.  But  as  the  evolu- 
tion of  heat  attends  almoft  all  chemical  combinations,  it  is  pro- 
bable, that  it  alfo  attends  the  fecretions  of  the  various  fluids  from 
the  blood  ; and  that  the  conftant  combinations  or  productions 
ol  new  fluids,  by  means  of  the  glands,  conftitutethe  more  gene- 
ral fource  of  animal  heat : this  feems  evinced  by  the  univerfal 
evolution  of  the  matter  of  heat  in  the  blufh  of  ftrame  or  of  an- 
ger ; in  which,  at  the  fame  time,  an  increaied  fecretion  of  the  per- 
Ipirable  matter  occurs ; and  the  partial  evolution  of  it  from  to- 
pical inflammations,  as  in  gout  or  rheumatifm,  in  which  there 
is  a fecretion  of  new  blood-veflels. 

Some  medical  philofophers  have  afccibed  the  heat  of  animal 

bodies 


OXYGENATION  SeCt.  XXXVUI.  2 : 


346 

bodies  to  thefridfion  of  the  particles  of  the  blood  againft  the  f.des 
of  the  veflels.  But  no  perceptible  heat  has  ever  been  produced 
by  the  agitation  of  water,  or  oil,  or  quickfilver,  or  other  fluids ; 
except  thofe  fluids  have  undergone,  at  the  fame  time,  fome  che- 
mical change,  as  in  agitating  milk  or  wine,  till  they  become  four. 

Betides  the  fuppoied  production  of  phofphoric  acid,  and 
change  of  colour  of  the  blood,  and  the  production  of  carbo- 
nic acid,  there  would  appear  to  be  fomething  of  a more  fubtile 
nature  perpetually  acquired  from  the  atmofphere;  which  is  too 
fine  to  be  long  contained  in  animal  veflels,  and  dierefore  re- 
quires perpetual  renovation ; and  without  which  life  cannot 
continue  longer  than  a minute  or  two : this  ethereal  fluid  is  pro- 
bably fecreted  from  the  blood  by  the  brain,  and  perpetually  dif- 
fipated  in  the  actions  of  the  mufcles  and  organs  of  fenfe. 

That  the  blood  acquires  fomething  from  the  air  which  is 
immediately  neceiTary  to  life,  appears  from  an  experiment  of 
Dr.  Hare,  (Philof.  Tranfact.  abridged,  vol.  iii.  p.  239.)  who 
found,  “ that  birds,  mice,  &c.  would  live  as  long  again  in  a 
veflfel,  where  he  had  crowded  in  double  the  quantity  of  air  by 
a condenfing  engine,  than  they  .did  when  confined  in  air  of 
the  common  denlity.”  Whereas,  if  lome  kind  of  deleterious 
vapour  only  was  exhaled  from  the  blood  in  refpiration,  the  air, 
when  condenfed  into  half  its  compafs,  could  not  be  fuppofed  to 
receive  fo  much  of  it. 

II.  Sir  Edward  Hulfe,  a phyfician  of  reputation  at  the  begin- 
ning of  the  prefent  century,  was  of  opinion,  that  the  placenta 
was  a refpiratorv  organ,  like  the  gills  of  rifh ; and  not  an  organ 
to  fupply  nutriment  to  the  fcetus,  as  mentioned  in  Derham’s 
Phyllco-theology.  Many  other  phyficians  feem  to  have  el- 
poufed  the  fame  opinion,  as  noticed  by  Haller.  Elem.  Phvfi- 
ologias,  T.  i.  Dr.  Gipfon  publifhed  a defence  of  this  theory 
in  the  Medical  Eflays  of  Edinburgh,  vol.  i.  and  ii.  which  doc- 
trine is  there  controverted  at  large  by  the  late  Alexander  Mon- 
ro ; and  fince  that  time  the  general  opinion  has  been,  that  the 
placenta  is  an  organ  of  nutrition  only,  owing,  perhaps,  radier 
to  the  authority  of  fo  great  a name,  than  to  the  validity  of  tire 
arguments  adduced  in  its  fupport.  The  iubjecf  has  lately  been 
relumed  by  Dr.  James  JefFray  and  Dr.  Forefter  French,  in  their 
inaugural  diflfertations,  at  Edinburgh  and  at  Cambridge,  who 
have  defended  the  contrary  opinion  in  an  able  and  ingenious 
manner,  and  from  whole  Thefes  I have  extracted  many  of  the 
following  remarks. 

Firit,  by  the  late  difcoveries  of  Dr.  Prieftlev,  M.  Lavoifier, 
and  other  philofophers,  it  appears,  that  the  balls  of  atmofpherical 
air,  called  oxygene,  is  received  by  the  blood  through  the  mem- 
branes 


Sect.  XXX VIII.  2. 


OF  BLOOD. 


341 

branes  of  the  lungs ; and  that,  by  this  addition,  the  colour  of  the 
blood  is  changed  from  a dark  to  a light  red.  Secondly,  that 
water  pofTefTes  oxygene  alfo,  as  a part  of  its  compofiticn,  and 
contains  air  likcwife  in  its  pores  : whence  the  blood  of  fifli  re- 
ceives oxygene  from  the  water,  or  from  the  air  it  contains,  by 
means  of  their  gills,  in  the  fame  manner  as  the  bloou  is  oxyge- 
nated in  the  lungs  of  air-breathing  animals:  it  changes  its  co- 
lour, at  the  fame  time,  from  a dark  to  a light  red,  in  the  vefTels 
of  their  gills,  which  conftitute  a pulmonary  organ,  adapted  to 
the  medium  in  which  they  live.  Thirdly,  that  the  placenta 
confifts  of  arteries  carrying  the  blood  to  its  extremities,  and  a 
vein  bringing  it  back,  fefembling  exactly,  in  ftrudbure,  the  lungs 
and  gills  above  mentioned ; and  that  the  blood  changes  its  colour, 
from  a dark  to  a light  red,  in  palling  through  thefe  vefTels. 

This  analogy  between  the  lungs  and  gills  of  animals,  and  the 
placenta  of  the  foetus,  extends  through  a great  variety  of  other 
circumftances  : thus,  air-breathing  Creatures  and  fifli  can  live 
but  a few  minutes  without  air  or  water,  or  when  they  are  con- 
fined in  fuc'h  air  or  water  as  has  been  fpoiled  by  their  own  re- 
fpiration : the  fame  happens  to  the  foetus,  which,  as  foon  as  the 
placenta  is  feparated  from  the  uterus,  muft  either  expand  its 
lungs,  and  receive  air,  of  die.  Hence,  from  the  ftrufcure,  as 
well  as  the  ufe  of  the  placenta,  it  appears  to  be  a refpiratory 
organ,  like  the  gills  of  fifli,  by  which  the  blood  in  the  foetus 
becomes  oxygenated. 

From  the  terminations  of  the  placental  vefTels  not  being  ob- 
ferved  to  bleed  after  being  torn  from  the  uterus,  while  tbofe  of 
the  uterus  effufe  a great  quantity  of  florid  arterial  blood,  the 
terminations  of  the  placental  vefTels  would  Teem  to  be  inferred 
into  the  arterial  ones  of  the  mother;  and  to  receive  oxygena- 
tion from  the  pafling  currents  of  her  blood  through  their  coats 
or  membranes  ; which  oxygenation  is  proved  by  the  change  of 
the  colour  of  the  blood  from  dark  to  light  red,  in  its  paflage 
from  the  placental  arteries  to  the  placental  vein. 

The  curious  ftru&ure  of  the  cavities,  or  lacunae  of  the  pla- 
centa, demonftrated  by  Mr.  J.  Hunter,  explains  this  circum- 
flance.  That  ingenious  philofopher  has  fhewn,  that  there  are 
numerous  cavities  or  lacunae  formed  on  that  fide  of  the  pla- 
centa, which  is  in  contact  with  the  uterus  ; ihofe  cavities  or 
cells  are  filled  with  blood  from  the  maternal  arteries  which 
- open  into  them  ; which  blood  is  again  taken  up  by  the  mater- 
nal veins,  and  is  thus  perpetually  changed:  while  the  termi- 
nations of  the  placental  arteries  and  veins  are  fpread  in  fine 
reticulation  on  the  fides  of  thefe  cells : and  thus,  as  the  grow- 
ing foetus  requires  greater  oxygenation,  an  apparatus  is  pro- 
duced reiembiing  exactly  the  air-cells  of  the  lungs. 


In 


m OXYGENATION  Sect.  XXXVIII.  31 

la  cows,  and  other  ruminating  animals,  the  internal  furface 
of  the  uterus  is  unequal,  like  hollow  cups,  which  have  been 
called  cotyledons ; and  into  thefe  cavities  the  prominencies  of 
the  numerous  placentas  with  which  the  foetus  of  thofe  animals 
is  furnilhed,  are  inferted,  and  ftrictly  adhere;  though  they  mav 
he  extracted  without  effufion  of  blood.  Thefe  inequalities  of 
the  uterus,  and  the  numerous  placentas  in  confequence,  feemed 
to  be  deligned  for  the  purpofe  of  expanding  a greater  furface  for 
the  terminations  ot  the  placental  vefTels,  for  the  purpofe  of  re- 
receiving oxygenation  from  the  uterine  ones;  as  the  progeny 
of  this  clafs  of  animals  are  more  completely  formed  before  their 
nativity,  than  that  of  the  carnivorous  clafles,  and  mufl  thence, 
in  the  latter  weeks  of  pregnancy,  require  greater  oxygenation. 
Thus  calves  and  lambs  can  walk  about  in  a few  minutes  after 
their  birth;  while  puppies  and  kittens  remain  many  days  with- 
out opening  their  eyes.  And  though  on  the  reparation  of  the 
cotyledons  of  ruminating  animals,  no  blood  is  efrufed,  yet  this 
is  owing  clearly  to  the  greater  power  of  contraction  of  their 
uterine  lacunae  or  alveoli.  See  Medical  EfTays,  vol.  v.  page 
144.  And  from  the  fame  caufe  they  are  not  liable  to  a fan- 
guiferous  menftruation. 

The  neceffity  of  the  oxygenation  of  the  blood  in  the  foetus 
is  farther  illuflrated  by  the  analogy  ot  the  chick  in  the  egg; 
which  appears  to  have  its  blood  oxygenated  at  the  extremities 
of  the  veffels  furrounding  the  yolk;  which  are  lpread  on  the 
air-bag  at  the  broad  end  of  the  egg,  and  may  abforb  oxvgene 
through  that  moift  membrane  from  the  air  confined  .behind  it;, 
and  which  is  fhewn,  by  experiments,  in  the  exhaufled  receiver, 
to  be  changeable  through  the  {hell. 

This  analogy  may  even  be  extended  to  the  growing  feeds  of 
vegetables ; which  were  fhewn,  by  Mr.  Scheele,  to  require  a re- 
novation of  the  air  over  the  water  in  which  they  were  con- 
fined. Many  vegetable  feeds  are  furrounded with  air  in  their 
pods  or  receptacles,  as  peas,  the  fruit  of  ftaphvlea,  and  lichnis 
veficaria : but  it  is  probable,  that  thofe  feeds,  after  they  are  fhed, 
as  well  as  the  fpawn  of  fill),  by  the  fituation  of  the  former  on  or 
near  the  moiit  and  aerated  furface  of  the  earth,  and  of  the  latter . 
in  the  ever-changing  and  ventilated  water,  may  not  be  in  need 
of  an  apparatus  for  the  oxygenation  of  their  tirfl  blood,  before 
the  leaves  of  one  and  the  gills  of  the  other  are  produced  for  this 
purpofe. 

111.  1.  There  are  many  arguments,  befides  the  ftridl  analogy 
between  the  liquor  amnii  and  the  albumen  ovi,  which  fliew  the 
former  to  be  a nutritive  fluid;  and  that  the  feetus,  in  the  latter 
months  of  pregnancy,  takes  it  into  its  llomach ; and  that,  in 

confequence, 


Sect.  XXXVIII.  3.  OF  BLOOD.  54.9 

confequence,  the  placenta  is  produced  for  fome  other  important 
purpofe. 

Firft,  that  the  liquor  arnnii  is  not  an  excrementitious  fluid, 
-is  evinced,  becaufe  it  is  found  in  greater  quantity,  when  the 
foetus  is  young,  decreafing  after  a certain  period  till  birth.  Hal- 
-ler  aflferts,  “ that  in  fome  animals,  but  a fmall  quantity  of  this 
fluid  remains  at  the  birth.  In  the  eggs  of  hens  it  is  confumed 
on  the  eighteenth  day,  fo  that,  at  the  exclusion  of  the  chick, 
fcarcely  any  remains.  In  rabbits,  before  birth,  there  is  none.” 
■Elem.  Phyflol.  Had  this  been  an  excrementitious  fluid,  the 
■contrary  would  probably  have  occurred.  Secondly,  the  fkin 
•of  the  fcetus  is  covered  with  a whitifh  cruft  or  pellicle,  which 
would  feem  to  preclude  any  idea  of  the  liquor  arnnii  being 
produced  by  any  exhalation  of  perlpirable  matter.  And  it 
cannot  conftft  of  urine,  becaufe,  in  brute  animals,  the  urachus 
paflfes  from  the  bladder  to  the  alantois  for  the  exprefs  purpofe  of 
•carrying  off  that  fluid  ; which,  however,  in  the  human  foetus, 
feems  to  be  retained  in  the  diftended  bladder,  as  the  feces  are 
accumulated  in  the  bowels  of  all  animals. 

2.  The  nutritious  quality  of  the  liquid  which  fur  rounds  the 
•foetus,  appears  from  the  following  conlideradons.  1.  It  is  co- 
agulable  by  heat,  by  nitrous  acid,  and  by  fpirit  of  wine,  like 
milk,  ferum  of  blcou,  and  other  fluids,  w'hich  daily  experience 
•evinces  to  be  nutritious.  2.  It  has  a faltifh  tafte,  according  to 
the  accurate  Baron  Haller,  not  unlike  the  whey  of  milk,  which 
it  even  refembles  in  fmell.  3.  The  white  of  the  egg,  which 
conftitutes  the  food  of  the  chick,  is  (hewn  to  be  nutritious  by 
our  daily  experience ; belldes  the  experiment  of  its  nutritious 
.cffefls,  mentioned  by  Dr.  Fordyce,  in  his  late  Treatife  on  Di- 
geftion,  p.  178;  who  adds,  that  it  much  refembles  the  e hernial 
parts  of  the  ferum  of  blood. 

3.  A fluid,  fimilar  to  the  fluid  with  which  the  fcetus  is  fur- 
rounded,  except  what  little  change  may  be  produced  by  a be- 
ginning digeftion,  is  found  in  the  ftomach  of  the  fcetus ; and 
the  white  of  the  egg  is  found,  in  the  fame  manner,  in  the  fto- 
mach of  the  chick. 

Numerous  hairs,  fimilar  to  thofe  of  its  fkin,  are  perpetually 
found  among  the  contents  of  the  ftomach  in  new-born  calves ; 
which  muft,  therefore,  have  licked  themfelves  before  their  na- 
tivity. Blafii  Anatom.  See  Se£t.  XVI.  2.  on  Inftindfc. 

The  chick  in  the  egg  is  feen  gently  to  move  in  its  furround- 
ing fluid,  and  to  open  and  lhut  its  mouth  alternately.  The 
fame  has  been  obferved  in  puppies.  Haller’s  El.  Phyf.  I.  8. 
p.  201. 

A column  of  ice  has  been  feen  to  reach  down  the  oefopha- 


350  OXYGENATION,  &c.  Sect.  XXXVIII.  3. 

gus,  from  the  mouth  of  the  ftomach,  in  a frozen  foetus ; and 
this  ice  was  the  liquor  amnii  frozen. 

The  meconium,  or  firft  feces,  in  the  bowels  of  new-born 
infants,  evince,  that  fomething  has  been  digefted;  and  what 
could  this  be  but  the  liquor  amnii,  together  with  the  recre- 
ments of  the  gaftric  juice  and  gall,  which  were  neccffary  for  its 
digeftion  ? 

There  have  been  recorded  fome  monftrous  births  of  animals 
■without  heads,  and  coniequently  without  mouths,  which  feem 
to  have  been  delivered  on  doubtful  authority,  or  from  inaccu- 
rate obiervation.  There  are  two  of  fuch  monftrous  produc- 
tions, however,  better  attefted  ; one  of  a human  foetus,  men- 
tioned by  Gipion,  in  the  Scots  Medical  Effays  ; which,  having 
the  gula  impervious,  was  furni (lied  with  an  aperture  into  the 
wind-pipe,  which  communicated  below  into  the  gullet ; by 
means  of  which  the  liquor  amnii  might  be  taken  into  the  fto- 
mach, before  nativity,  without  danger  of  fuffocation,  while  the 
foetus  had  no  occafton  to  breathe.  The  other  monftrous  toetus 
is  deferibed  by  Vander  Wiel,  who  affects,  that  he  faw  a mon- 
ftrous lamb,  which  had  no  mouth  ; but  inftead  of  it  was  fur- 
nifhed  with  an  opening  in  the  lower  part  of  the  neck  into  the 
ftomach.  Both  thefe  inftances  evidently  favour  the  doctrine  of 
the  feetus  being  nourifhed  by  the  mouth  ; as  otherwise  there 
had  been  no  neceftity  for  new  or  unnatural  apertures  into  the 
ftomach,  when  the  natural  ones  were  deficient. 

From  thefe  fadts  and  obfervations  we  may  fafelv  infer,  that 
the  fetus  in the  womb  is  nourifhed  by  the  fluid  which  furrounds 
it ; which, during  the  firft  period  of  geftation,  is  abforbed  by  the 
naked  lacteals ; and  is  afterwards  fwallowed  into  the  ftomach 
and  bowels,  when  thefe  organs  are  perfected  ; and  iaftly,  that 
the  placenta  is  an  organ  for  the  purpofe  ot  giving  due  oxygena- 
tion to  the  blood  of  the  fetus ; which  is  more  neceffarv,  or  at 
leaf!  more  frequently  neceflary,  than  even  the  fupply  of  food. 

The  queftion  of  the  great  Harvey  becomes  thus  eafily  an- 
fwered.  “ Why  is  not  the  fetus  in  the  womb  fuft'oeated  for 
want  of  air,  when  it  remains  there  even  to  the  tenth  month 
without  refpiration:  yet,  if  it  be  bom  in  the  feventh  or  eighth 
month,  and  has  once  refpired,  it  becomes  immediately  futfocat- 
ed  for  want  of  air,  if  its  refpiration  be  obftrudted?” 

For  further  information  on  this  fubjedt,  the  reader  is  referred 
to  theTentamen  Medicum  of  Dr.  Jeffray,  printed  at  Edinburgh 
in  1786.  And  it  is  hoped  that  Dr.  French  will  fome  time  give 
his  thefes  on  this  fuhjedfc  to  the  public. 


SECT. 


.Sect.  XXXIX. 


OF  GENERATION. 


35 1 


SECT.  XXXIX. 

OF  GENERATION. 

Felix,  qui  causas  alta  caligine  raersas 

Pandit,  et  evolvit  tenuissima  vincula  rerum.  Anon. 

I.  Habits  of  aiding  and  feeling  of  individuals  attend  the 
foul  into  a future  life,  and  attend  the  new  embryon  at  the 
time  of  its  ■production.  The  new  [peck  of  entity  abforbs 
nutriment , and  receives  oxygene.  Spreads  the  terminations 
of  its  veffels  en  cells,  which  communicate  with  the  arteries 
of  the  uterus  ; fometimes  with  thofe  of  the  peritoneum. 
Afterwards  it  f wallows  the  liquor  amnii,  which  it  produces 
by  its  irritation  from  the  uterus,  or  peritoneum.  Like 
infeCts  in  the  heads  of  calves  and  fieep.  Why  the  white 
of  egg  is  of  tvjo  conflflencies.  Why  nothing  is  found  in 
quadrupeds  flmilar  to  the  yolk,  nor  in  mof  vegetable  feeds. 
II.  i.  Eggs  of  frogs  and  fifi  impregnated  out  of  their  bo- 
dies. Eggs  of  fowls  which  are  not  fecundated,  contain 
only  the  nutriment  for  the  embryon.  The  embryon  is  pro- 
duced by  the  male,  and  the  nutriment  by  the  female.  Ani- 
malcula  in  femine.  Profujion  of  nature's  births.  2.  Ve- 
getables viviparous.  Buds  and  bulbs  have  each  a father , 
but  no  mother.  V effels  of  the  leaf  and  bud  inofculate. 
The  paternal  offspring  exactly  rejembles  the  parent.  3. 
Inf e As  impregnated  for  fix  generations.  Polypus  branches 
like  buds.  Creeping  roots.  Viviparous  flowers.  Tcenia , 
volvox.  Eve  from  Adam' s rib.  Semen  not  a flimulus  to 
the  egg.  III.  1.  Embryons  not  originally  created  within 
other  embryons.  Organized  matter  is  not  fo  minute.  2. 
All  the  parts  of  the  embryon  are  not  formed  in  the  male 
parent.  Crabs  produce  their  legs ; worms  produce  their 
heads  and  tails.  In  wens,  cancers  and  inflammations,  new 
veffels  are  formed.  Mules  partake  of  the  forms  of  both 
parents.  Hair  and  nails  grow  by  elongation,  not  by  dif- 
tention.  3.  Organic  particles  of  Buffon.  IV.  I.  Rudi- 
ment of  the  embryon  a flmple  living  filament-,  becomes  a 
living  ring,  and  then  a living  tube.  2.  It  acquires  neiv 
irritabilities,  and fenfibilities  with  new  organizations,  as 
in  wounded  fnails,  polypi,  moths , gnats,  tadpoles.  Hence 
new  parts  are  acquired  by  addition , not  by  diflention.  3. 
All  parts  of  the  body  grow,  if  not  confined.  4.  Fcetufcs 
deficient  at  their  extremities,  or  have  a duplicature  of 
parts.  Monfltvous  births.  Double  parts  of  vegetables » 
* 5.  Mules 


OF  GENERATION.  Sect.  XXXIX.  i. 


352 

5.  Mules  cannot  be  formed  by  difiention  of  the  fenunal  ens. 

6.  Families  of  animals  from  a mixture  of  their  orders. 

Mules  imperfedt.  7.  Animal  appetency  like  chemical  af- 
finity. Vis  fabricatrix  and  medicatrix  of  nature.  8.  The 
changes  of  animals  before  and  after  nativity.  Similarity 
■of  their  firudiure.  Changes  in  them  from  lujl , hunger,  and 
danger.  All  warm-blooded  animals  derived  from  one  liv- 
ing filament.  Cold-blooded  animals,  infects,  worms,  ve- 
getables, derived  alfo  from  one  living  filament.  Male 
animals  have  teats.  Male  pidgeon  gives  milk.  The 
world  itfclf  generated.  Tile  ccufe  of  caufes.  A fiate 
of  probation  and  refponfibility.  V.  1.  Efficient,  can) e of 
the  colours  of  birds  eggs,  and  of  hair  and  feathers,  which 
become  white  in  fnowy  countries.  Imagination  of  the  fe- 
male colours  the. egg.  Ideas  or  motions  of  the  retina  imi- 

tated by  the  extremities  of  the  nerves  of  touch,  or  rite 
mucofum.  2.  Nutriment  Jupplied  by  the  female  of  three 
kinds.  Her  imagination  can  ortly  affedi  the  firjl  kind. 
Mules  how  produced,  and  mulattoes.  Organs  of  re-pro- 

• dudtion  why  deficient  in  mules.  Eggs  with  double  yolks. 
VI.  I.  Various  fccretions  produced  by  the  extremities  of 
the  vcfficls , as  in  the  glands.  Contagious  matter.  Many 
glands  afi'edied  by  pleafurcable  ideas , as  thefe  which  fe- 
crete  the  femen.  1.  Snails  and  worms  are  hermaphrodite, 
yet  cannot  impregnate  themfelves.  Final  caufe  of  this. 
3.  The  imagination  of  the  male  forms  the  fex.  Ideas , or 
motions  of  the  nerves  of  vifion  or  of  touch , are  imitated  by 
the  ultimate  extremities  of  the  glands  of  the  tefies,  which 
mark  the  fex.  This  effedi  of  the  imaginat  ion  belongs  only 
to  the  male.  The  fex  of  the  embryon  is  not  owing  to  acci- 
dent. 4.  Caufes  of  the  changes  in  animals  from  imagina- 
tion, as  in  monfers.  From  the  male.  From  the  female.  5. 
Mifcarriages  from  fear.  6.  Power  of  the  imagination 
of  the  male  over  the  colour  .form,  and  fex  of  the  progeny. 
An  infiance  of  it.  7.  Adi  of  generation  accompanied  with 
ideas  ef  the  male  or  female  form.  Art  of  begetting  beau- 
tiful children  of  cither  fex.  VII.  Recapitulation.  VIII. 
Conclufion.  Of  caufe  and  effedi.  The  atomic  philo f op hy 
leads  to  a fir ft  caufe. 

1.  THE  ingenious  Dr.  Hartley,  in  his  work  on  man,  and  fome 
other  philofophers,  have  been  ot  opinion,  that  our  immortal  part 
acquires,  during  this  life,  certain  habits  of  action  or  of  Sentiment, 
which  become  for  ever  indiffoluble,  continuing  after  death  in  a 
ifuture  fiate  of  exigence;  and  add,  that  if  thefe  habits  are  of  the 

malevolent 


OF  GENERATION. 


Sect.  XXXIX.  r. 

■ 


SS3 


malevolent  kind,  they  mult  render  the  poffeffor  miferable  even- 
in  heaven.  I would  apply  this  ingenious  idea  to  the  generation 
or  production  of  the  embryon,  or  new  animal,  which  partakes 
fo  much  of  the  form  and  propenfities  of  the  parent. 

Owing  to  the  imperfection  of  language  the  offspring  is  term- 
ed a new  animal,  but  is  in  truth  a branch  or  elongation  of  the 
parent  - fince  a part  of  the  embryon-animal  is,  or  was,  a part 
of  the  parent ; and  therefore,  in  ftriCt  language,  it  cannot  be  fa  id 
to  be  entirely  new  at  the  time  of  its  production ; and  therefore 
it  may  retain  fome  of  the  habits  of  the  parent- fyftem. 

At  the  earlieft  period  of  its  exiftence  the  embryon,  as  fecret- 
ed  from  the  blood  of  the  male,  would  feem  to  confift  of  a living 
filament,  with  certain  capabilities  of.  irritation,  fenfation,  voli- 
tion, and  affociation  ; and  alfo  with  fome  acquired  habits  or 
propenfities  peculiar  to  the  parent : the  former  of  thele  are  in 
common  with  other  animals;  the  latter  feem  to  diftinguifh  or 
produce  the  kind  of  animal,  whether  man  or  quadruped,  with 
the  fimilarity  of  feature  or  form  to  the  parent.  It  is  difficult  to 
be  conceived,  that  a living  entity  can  be  feparated  or  produced 
from  the  blood  by  the  action  of  a gland,  and  which  fhall  after- 
wards become  an  animal  fimilar  to  that  in  whofe  veffels  it  is 
formed  ; even  though  we  Should  fuppofe,  with  fome  modern  the- 
orifts,  that  tire  blood  is  alive ; yet  every  other  hypothecs  concern- 
ing genration  reds  on  principles  ftiil  more  difficult  to  our  com- 
pre  henfion. 

- At  the  time  of  procreation  this  fpeck  of  entity  is  received  in- 
to an  appropriated  nidus,  in  which  it  rnuft  acquire  two  circum- 
ftances  neceffary  to  its  life  and  growth  ; one  of  thefe  is  food  or 
fuflenance,  which  is  to  be  received  by  the  abforbent  mouths 
of  its  veffels  ; and  the  other  is  that  part  of  atmofpherical  air,  or 
of  water,  which,  by  the  new  chemiftry,  is  termed  oxygene,  and 
which  affeCts  the  blood  by  paffing  through  the  coats  of  the  vef- 
fels which  contain  it.  The  fluid  furrounding  the  embryon  in 
its  new  habitation,  which  is  called  liquor  amnii,  fupplies  it  with 
nourifhment;  and  as  fome  air  cannot  but  be  introduced  into 
the  uterus  along  with  the  ne\<7  embryon,  it  would  feem  that  this 
fame  fluid  would,  tor  a fhort  time,  fuppofe  for  a few  hours,  fup- 
ply  likewife  a fufficient  quantity  of  the  oxygene  for  its  immedi- 
ate exiftence. 

On  this  account  the  vegetable  impregnation  of  aquatic  plants 
is  performed  in  the  air;  and  it  is  probable  that  the  honey-cup, 
or  neCtary  of  vegetables,  requires  to  be  open  to  the  air,  that  the 
anthers  and  ftigmas  of  the  flower  may  have  food  of  a more  ox- 
ygenated kind  than  the  common  vegetable  fap-juice. 

On  the  introduction  ox  this  primordium  of  entity  into  the  ute- 
rus, 


354  OF  GENERATION.  Sect.  XXXIX.  f. 

rus,  the  irritation  of  the  liquor  amnii,  which  furrounds  it,  ex- 
cites the  abforbent  mouths  of  the  new  veflels  into  action  ; they 
drink  up  a part  of  it,  and  a pleafureable  fenfation  accompanies 
this  new  a£tion ; at  the  fame  time  the  chemical  affinity  of  the 
oxygene  a£ts  through  the  veflels  of  the  rubefcent  blood  ; and  a 
previous  want,  or  difagreeable  fenfation,  is  relieved  by  this  pro- 
cefs. 

As  the  want  of  this  oxygenation  of  the  blood  is  perpetual, 
(as  appears  from  the  inceflant  necefiitv  of  breathing  by  lungs 
or  gills)  the  veflels  become  extended  by  the  efforts  of  pain  or 
delire  to  feek  this  neceffary  object  of  oxygenation,  and  to  re- 
move the  difagreeable  fenfation  which  that  want  occafions. 
At  the  fame  time  new  panicles  of  matter  are  abforbed,  or  applied 
10  thefe  extended  veflels,  and  they  become  permanently  elongat- 
ed, as  the  fluid  in  contact  with  them  loon  lofes  the  oxygenous 
part  which  it  at  tirft  poffeffed,  which  was  owing  to  the  intro- 
duction of  air  along  with  the  embryon.  Thele  new  biood- 
veffels  approach  the  tides  of  the  uterus,  and  penetrate,  with 
their  tine  terminations,  into  the  veflels  of  the  mother,  or  adhere 
to  them,  acquiring  oxvgene,  through  their  coats,  from  the  paf- 
fmg  currents  of  the  arterial  blood  of  the  mother.  See  SecL 
XXXVUI.  2. 

This  attachment  of  the  placental  veflels  to  the  internal  fide 
of  the  uterus,  by  their  own  proper  efforts,  appears  further  iiiuf- 
tratedby  the  many  inftances  of  extra-uterine  foetules  which  have 
thus  attached  or  inferted  their  veflels  into  the  peritoneum,  or 
on  the  vifeera,  exactly  in  the  fame  manner  as  they  naturally 
infert  or  attach  them  to  the  uterus. 

The  abforbent  veflels  of  the  embryon  continue  to  drink  up 
nouriflrment  from  the  fluid  in  which  they  l'wim,  or  liquor  am- 
nii ; and  which  at  firfl:  needs  no  previous  digeftive  preparation  ; 
but  which,  when  the  whole  apparatus  ot  digeftion  beeon.es 
complete,  is  fwallowed  by  the  mouth  into  the  ftomach,  and 
being  mixed  with  faliva,  gaflric  juice,  bile,  pancreatic  juice, 
and  mucus  of  the  inteftines,  becomes  digefted,  and  leaves  a re- 
crement, which  produces  the  firfl:  fleces  of  die  infant,  called 
meconium. 

The  liquor  amnii  is  fecreted  into  the  uterus,  as  the  feetus  re- 
quires it,  and  may  probably  be  produced  by  the  irritation  ot  the 
feetus,  as  an  extraneous  body  ; fince  a fimilar  fluid  is  acquired 
from  the  peritoneum  in  cafes  of  extra-uterine  geftation.  fl  he 
young  caterpillars  of  the  gad-fly,  placed  in  the  fkins  ot  cows, 
and  the  young  of  the  ichneumon-flv,  placed  in  the  backs  of  the 
caterpillars  on  cabbages,  l'eern  to  produce  their  nourifhment  by 
their  irritating  the  iides  of  their  nidus.  A vegetable  iccretion 


Sect.  XXXIX.  i. 


OF  GENERATION". 


355 

and  concretion  is  thus  produced  on  oak -leaves,  by  the  gall-in- 
feci,  and  by  the  cynips  in  the  bedeguar  of  the  rofe;  and  by  the 
young  grafshopper  on  many  plants,  by  which  the  animal  fur- 
rounds  itfelf  with  froth.  But  in  no  circumftance  is  extra-ute- 
rine geftation  i'o  exactly  refembled  as  by  the  eggs  of  a fly, 
which  are  depoftted  in  the  frontal  finus  of  fheep  and  calves. 
Thefe  eggs  float  in  foine  ounces  of  fluid,  collected  in  a thin 
pellicle  or  hydatide.  This  bag  of  fluid  comprefTes  the  optic 
nerve  on  one  fide,  by  which  the  vilion  being  lei's  diftindt  in  that 
eye,  the  animal  turns,  in  perpetual  circles,  towards  the  fide  af- 
fecfted,  in  order  to  get  a more  accurate  view  of  objedts ; for  the 
fame  reafon  as  in  fquinting  the  affedted  eye  is  turned  away  from 
the  object  contemplated.  Sheep,  in  the  warm  months,  keep 
their  nofes  clofe  to  die  ground,  to  prevent  this  fly  from  i'o  rea- 
dily getting  into  their  noftrils. 

The  liquor  aranii  is  fecreted  into  the  womb  as  it  is  required, 
not  only  in  refpedt  to  quantity,  but,  as  the  digeftive  powers  of 
the  foetus  become  formed,  this  fluid  becomes  of  a different  con- 
fidence and  quality,  till  it  is  exchanged  for  milk  after  nativity. 
Haller.  Phyfiol.  V.  I.  In  the  egg  the  white  part,  which  is 
analogous  to  the  liquor  amnii  of  quadrupeds,  coniifts  of  two 
diftindt  parts ; one  of  which  is  more  vifcid,  and  probably  more 
difficult  of digeftion,  and  more  nutritive  than  the  other;  and  this 
latter  is  ufed  in  the  laft  week  of  incubation.  The  yolk  of  the 
egg  is  a ftiil  ftronger  or  more  nutritive  fluid,  which  is  drawn  up 
into  the  bowels  of  the  chick,  juft  at  its  exciufton  from  the  {hell, 
and  ferves  it  for  nourifhment  for  a day  or  two,  till  it  is  able  to 
digcft,  and  has  learnt  to  c’nufe  the  harder  feeds  or  grains,  which 
are  to  afford  it  fuftenance.  Nothing  analogous  to  this  yolk  is 
found  in  the  foetus  of  lactiferous  animals,  as  the  milk  is  another 
nutritive  fluid  ready  prepared  for  the  young  progeny. 

The  yolk,  therefore,  is  not  r.eceflary  to  the  fpawn  of  fifh,  the 
eggs  of  infects,  or  for  the  feeds  of  vegetables ; as  their  embry- 
ons  have  probably  their  food  prefented  to  them  as  foon  as  they 
are  excluded  from  their  fhells,  or  have  extended  their  roots. 
Whence  it  happens,  thatfome  infedts  produce  a living  progeny 
in  the  fpriiig  and  fummer,  and  eggs  in  the  autumn ; and  foma 
vegetables  have  living  roots,  or  buds,  produced  in  the  place  of 
feeds,  as  the  polygonum  viviparum,  and  magical  onions.  See, 
Botanic  Garden,  P.  11.  art.  anthoxanthum. 

There  feems,  however,  to  bearel'ervoir  of  nutriment  prepar- 
ed for  fome  feeds  befides  their  cotyledons  or  feed-leaves,  which 
may  be  fuppofed  in  fome  meafure  analogous  to  the  yolk  of  the 
egg.  Such  are  the  faccharine  juices  of  apples,  grapes  and  other 
fruits,  which  fupply  nutrition  to  the  feeds  after  they  fall  on  the 

Ah  ground. 


OF  GENERATION.  Sect.  XXXIX'.  t. 

ground.  And  fuch  is  the  milky  juice  in  the  centre  of  the  co- 
coa-nut, and  part  of  die  kernel  of  it;  rhe  fame  I fuppofe  of  all 
other  monocotyledon  feeds,  as  of  the  palms,  grades,  and  lilies. 

II.  i.  The  procefs  of  generation  is  ftill  involved  in  impene- 
trable obfcurity  ; conjectures  may  neverthelefs  be  formed  con- 
cerning fome  of  its  circumftances.  Fir  ft,  the  eggs  of  fifh  and 
frogs  are  impregnated,  after  they  leave  the  body  of  the  female  : 
bccaufe  they  are  depofited  in  a fluid,  and  are  not  therefore  c co- 
vered with  a hard  {hell.  It  is,  however,  remarkable,  that  nei- 
ther frogs  nor  hfh  will  part  with  their  fpawn  without  the  pie- 
fence  of  the  male ; on  which  account  female  carp  and  goid-hfh 
in  fmall  ponds,  where  there  are  no  ipales,  frequently  die  from 
the  diftention  of  their  growing  fpawn.  2.  The  eggs  of  fowls, 
which  are  laid  without  being  impregnated,  are  feen  to  contain 
only  the  yolk  and  -white,  wrhich  are  evidently  the  food  or  fufle- 
nance  for  the  future  chick.  3.  As  the  cicatricuia  of  thefe  eggs 
is  given  by  the  cock,  and  is  evidently  the  rudiment  of  the  new 
animal,  we  may  conclude,  that  the  ^embryon  is  produced  by 
the  male,  and  the  proper  food  and  nidus  by  the  female.  For  if 
the  female  be  fuppofed  to  form  an  equal  part  of  the  embryon, 
why  fhould  fhe  form  the  whole  of  the  apparatus  for  nutri- 
ment and  for  oxygenation  ? The  male  in  many  animals  is  lar- 
ger, ftronger,  and  digefts  more  food  than  the  female,  and  there- 
fore fhould  contribute  as  much  or  more  towards  the  re-produc- 
tion of  the  fpccies  ; but  if  he  contributes  only  half  the  embryon, 
and  none  of  the  apparatus  for  fuftenance  and  oxygenation, 
the  divifion  is  unequal ; the  flrength  of  the  male  and  his  con- 
fumption  of  food  are  too  great  for  the  effedf,  compared  with 
that  of  the  female,  which  is  contrary  to  the  ufual  courfe  of 
nature. 

In  objection  to  this  theory  of  generation  it  may  be  faid,  if 
the  animalcula  in  femine,  as  feen  bv  tire  microfcope,  be  all  of' 
them  rudiments  of  homunculi,  when  but  one  of  them  can  find 
a nidus,  what  a wade  nature  has  made  ol  her  productions  ? 

I do  not  affert  that  thefe  moving  particles,  vifible  by  the  mi- 
crolcope,  are  hemunciones ; perhaps  they  may  be  the  creatures 
of  ftagnation  or  putridity,  or  perhaps  no  creatures  at  all ; but  if 
they  are  fuppofed  to  be  rudiments  of  homunculi,  or  embrvons, 
fuch  a profufion  of  them  correfponds  with  the  general  efforts 
of  nature  to  provide  for  the  continuance  of  her  fpecies  of  ani- 
mals. Everv  individual  tree  produces  innumerable  feeds,  and 
every  individual  fifh  innumerable  ipawn,  in  fuch  inconceive- 
able  abundance  as  would,  in  a fhort  fpace  of  time,  crowd  the  earth 
and  ocean  with  inhabitants ; and  thefe  are  much  more  perfeeff 
animals  than  the  animalcula  in  femine  can  be  fuppofed  to  be, 


.‘Sect.  XXXIX.  2.  OF  GENERATION.  -357 

and  perifh  in  uncounted  millions.  This  argument  only  ftrews, 
that  the  productions  of  nature  are  governed  by  general  laws  ; 
and  that,  by  a wife  fuperfluity  ofproviiion,  fhe  has  enfured  their 
continuance. 

2.  That  the  embryon  is  fecreted  or  produced  by  the  male, 
and  not  by  the  conjunction  of  fluids  from  both  male  and  fe- 
male, appears  from  the  analogy  of  vegetable  feeds.  In  the  large 
flowers,  as  the  tulip,  there  is  no  flmilarity  of  apparatus  between 
the  anthers  and  the  ftigma ; the  feed  is  produced,  according  to 
the  obfervations  of  Spallanzani,  long  before  the  flowers  open, 
and,  in  confequence,  long  before  it  can  be  impregnated,  like  the 
egg  in  the  pullet.  And  after  the  prolific  duft  is  (lied  on  the 
ftigma,  the  feed  becomes  coagulated  in  one  point  fit  ft,  like  the 
-cicatricula  of  the  impregnated  egg.  See  Botanic  Garden,  Part 
I.  additional  note  38,.  Now,  in  thefe  Ample  products  of  na- 
ture, if  the  female  contributed  to  produce  the  new  embryon 
equally  with  the  male,  there  would  probably  have  been  fome 
viable  flmilarity  of  parts  for  this  purpofe,  befides  thofe  necef- 
fary  for  the  nidus  and  fuftenance  of  the  new  progeny.  Befides, 
in  many  flowers  the  males  are  more  numerous  than  the  females, 
or  than  the  feparate  uterine  cells  in  their  germs,  w hich  would 
flhew  that  the  office  of  the  male  was  at  leaft  as  important  as 
that  of  the  female  ; whereas,  it  the  female,  befides  producing 
the  egg  or  feed,  was  to  produce  an  equal  part  of  the  embryon, 
file  office  of  re -production  would  be  unequally  divided  between 
them. 

Add  to  this,  that,  in  the  moft  Ample  kind  of  vegetable  re- 
production, I mean  the  buds  of  trees,  which  are  their  vivipa- 
rous offspring,  the  leaf  is  evidently  the  parent  of  the  bud, .which 
-rifes  in  its  bofom,  according  to  the  obfervation  of  Linnaeus. 
This  leaf  confifts  of  abfor'oent  veffels,  atrd  pulmonary  ones,  to 
-obtain  its  nutriment,  and  to  impregnate  it  with  oxygene.  This 
Ample  piece  of  living  organization  is  alfo  furnilhed  with  a 
power  of  re- production ; and  as  the  newr  offspring  is  thus  fup- 
ported,  adhering  to  its  father,  it  needs  no  mother  to  fupply  it 
with  a nidus,  and  nutriment,  and  oxygenation;  and  hence  no 
female  leaf  has  exiftence. 

I conceive,  that  the  veffels  between  the  bud  and  the  leaf 
communicate  or  inofculate ; and  that  the  bud  is  thus  ferved  with 
vegetable  blood,  that  is,  with  both  nutriment  and  oxygenation, 
•till  the  death  of  the  parent  leaf  in  autumn : and  in  this  refpeCt 
it  differs  from  the  fcetus  of  viviparous  animals.  Secondly,  that 
then  the  bark-veffels  belonging  to  the  dead-leaf,  and  in  which 
1 luppofe  a kind  of  manna  to  have  been  depofited,  become  now 
ifle  placental  veffels,  if  they  may  be  fo  called,  of  the  new  bud. 

From 


OF  GENERATION.  Sect.  XXXIX.  2. 


35^ 

From  the  vernal  lap,  thus  produced,  of  one  fugar-maple-tree 
in  Nevv-York  and  in  Pennfylvania,  live  or  fix  pounds  ot  good 
fugar  may  be  made  annually,  without  deftroying  the  tree. 
Account  of  Maple-fugar,  by  B.  Rufh.  London,  Phillips.  (See 
Botanic  Garden,  Parc  I.  additional  note  on  vegetable  placenta- 
tipn.) 

Thefe  velfels,  when  the  warmth  of  the  vernal  fun  hatches 
the  young  bud,  ferve  it  with  a faccharine  nutriment,  tii!  it  ac- 
quires leaves  ot  its  own,  and  (hoots  a new  fyftem  of  abforfcents 
down  the  bark  and  root  of  the  tree,  juft  as  the  farinaceous  or 
oily  matter  in  feeds,  and  the  faccharine  matter  in  fruits,  ferve 
their  embryons  with  nutriment,  till  thev  acquire  leaves  and 
roots.  This  analogy  is  as  forcible,  in  fo  obfcure  a fubject,  as  it 
is  curious ; and  may,  in  large  buds,  as  of  the  horfe-chefut,  be 
almoft  feen  by  the  naked  eye,  if,  with  a penknife,  the  remain- 
ing rudiment  of  the  laft  year’s  leaf,  and  of  the  new  bud  in  its 
bofom,  be  cut  away,  llice  by  flice.  The  feven  ribs  of  the  laft 
year’s  leaf  will  be  feen  to  have  aril'en,  from  the  pith,  in  (even 
diftinff  points,  making  a curve ; and  the  new  bud  to  have  been 
produced  in  their  centre,  and  to  have  pierced  the  alburnum  and 
cortex,  and  gi  own  without  the  afliftance  of  a mother.  A limilar 
procefs  may  be  ieen  on  differing  a tulip-root  in  winter:  the 
leaves  which  incloled  the  laft  year’s  flower-ftalk  were  not 
neceflary  for  the  flower;  but  each  of  thefe  was  the  father  of  a 
new  bud,  which  may  be  now'  found  at  its  bale,  and  which,  as  it 
adheres  to  the  parent,  requires  no  mother. 

This  paternal  offspring  of  vegetables,  I mean  their  buds  and 
bulbs,  is  attended  with  a very  curious  circumftance ; and  that 
is,  that  they  exactly  refemble  their  parents,  as  is  oblervable  in 
grafting  fruit-trees,  and  in  propagating  flower-roots ; whereas 
the  ieminal  offspring  of  plants,  being  fupplied  with  nutriment 
by  the  mother,  is  liable  to  perpetual  variation.  Thus,  alfo.  in 
the  vegetable  clafs  dioicia,  where  the  male  flowers  are  produced 
on  one  tree  and  the  female  ones  on  another,  the  buds  of  the 
male  trees  uniformly  produce  either  male  flowers,  or  other  buds 
limilar  to  themfelves,  and  the  buds  of  the  female  trees  produce 
either  female  flowers,  or  other  buds  limilar  to  themfelves ; 
■whereas  the  feeds  of  thefe  trees  produce  either  male  or  female 
plants.  From  this  analogy  of  the  production  of  vegetable  buds 
without  a mother,  I contend,  that  the  mother  does  not  contri- 
bute to  the  formation  of  the  living  ens  in  animal  generation, 
but  is  neceflliry  only  for  fupplying  its  nutriment  and  ox vge na- 
tion. 

There  is  another  vegetable  ia£t  published  by  M.  Koelreuter, 
■which  he  calls  “ a complete  metanlor'phofls  of  one  natural 

lpecjes 


Sect.  XXXIX.  2. 


OF  GENERATION. 


3.59 

fpecies  of  plants  into  another,”  which  (hews,  that  in  feeds  as 
well  as  in  buds,  the  embryon  proceeds  from  the  male  parent, 
though  the  form  of  the  fubfequent  mature  plant  is  in  part  de- 
pendent on  the  female.  M.  Koelreuter  impregnated  a ftigma 
of  the  nicotiana  ruftica  with  the  farina  of  the  nicotiana  pani- 
cu'.at?,,  and  obtained  prolific  feeds  from  it.  With  the  plants 
which  fprurig  from  thefe  feeds,  he  repeated  the  experiment,  im- 
pregnating them  with  the  farina  of  the  nicotiana  paniculata. 
As  the  mule  plants  which  he  thus  produced  were  prolific,  he 
continued  to  impregnate  them,  for  many  generations,  with  the 
farina  of  the  nicotiana  paniculata,  and  they  became  more  and 
more  like  the  male  parent,  till  he  at  length  obtained  fix  plants 
in  every  refpeft  perfectly  fimilar  to  the  nicotiana  paniculata, 
and  in  no  refpefl  refembling  their  female  parent  the  nicotiana 
ruftica.  Blumcnbach  on  Generation. 

3.  It  is  probable  that  the  infefts  which  are  faid'  to  require 
but  one  impregnation  for  fix  generations,  as  the  aphis  (fee 
Amenit.  Academ.)  produce  their  progeny  in  the  manner  above 
xlefcribed;  that  is,  without  a mother,  and  not  without  a father; 
and  thus  experience  a lucina  fine  ccncubitu.  Thofe  who  have 
attended  to  the  habits  of  the  polypus,  which  is  found  in  the 
ftagnant  water  of  our  ditches  in  July,  affirm  that  the  young 
ones  branch  out  from  the  fide  of  the  parent  like  the  buds  of 
trees,  and  after  a time  feparate  themfelves  from  them.  This 
is  fo  analogous  to  the  manner  in  which  the  buds  of  trees  ap- 
pear to  be  produced,  that  thefe  polypi  may  be  confidered  as  all 
male  animals,  producing  embryons,  which  require  no  mother 
to  fupply  them  with  a nidus,  or  with  nutriment,  and  oxyge- 
nation. 

This  lateral  or  lineal  generation  of  plants,  not  only  obtains 
in  the  buds  of  trees,  which  continue  to  adhere  to  them,  but  is 
beautifully  feen  in  die  wires  of  knot-grafs,  polygonum  avicu- 
lare,  and  in  thofe  of  ftrawberries,  rragaria  vefca.  In  thefe  an 
.elongated  creeping  bud  is  protruded,  and,  where  it  touches  the 
ground,  takes  root,  and  produces  a new  plant  derived  from  its 
lather,  from  which  it  acquires  both  nutriment  and  oxygenation, 
and,  in  confequence,  needs  no  maternal  apparatus  for  thefe  pur- 
pofes.  In  viviparous  flowers,  as  thofe  of  allium  magicum,  and 
polygonum  viviparum,  the  anthers  and  the  ftigmas  become  ef- 
fete and  perifli;  and  the- lateral  or  paternal  ofrsping  fucceeds 
inftead  of  feeds,  which  adhere  tiil  they  are  fufficiently  mature, 
.and  then  fall  upon  the  ground,  and  take  root  like  other  bulbs. 

The  lateral  production  of  plants  by  wires,  while  each  new 
plant  is  thus  chained  to  its  parent,  and  continues  to  put  forth 
another  and  another,  as  the  wire  creeps  onward  on  the  ground, 

is- 


55o  OF  GENERATION.  Sect.  XXXIX.  3. 

is  exactly  refembled  by  the  tape-worm,  or  taenia,  fo  often  found 
in  the  bowels,  ftretching  itfelf  in  a chain  quite  from  the  fto- 
inach  to  the  redtum.  Linnaeus  afferts,  “ that  it  grows  old  at 
one  extremity,  while  it  continues  to  generate  young  ones  at  the 
other,  proceeding  ad  infinitum,  like  a root  cf  grafs.  The  fe- 
parate  joints  are  called  gourd-worms,  and  propagate  new  joints, 
like  the  parent,  without  end;  each  joint  being  furnifhed  with 
its  proper  mouth  and  organs  of  digeftion.”  Syftema  Naturae. 
Vermes  Tenia.  In  this  animal  there  evidently  appears  a power 
of  re-production,  without  any  maternal  apparatus  for  thepur- 
pofe  of  fupplying  nutriment  and  oxygenation  to  the  embrvon, 
as  it  remains  attached  to  its  father  till  its  maturity.  The  voivox 
globator,  which  is  a .tranfparen:  animal,  is  faid,  by  Id  nose  us, 
to  bear  within  it  fons  and  grand-fons  to  the  fifth  generation, 
Thefe  are  piobably  living  faetufes,  produced  by  the  father,  of 
different  degrees  of  maturity,  to  be  detruded  at  different  periods 
of  time,  like  the  unimpregnated  eggs,  of  various  fizes,  which 
are  found  in  poultry;  and,  as  they  are  produced  without  any 
known  copulation,  contribute  to  evince,  that  the  living  embrvon 
in  other  orders  of  animals  is  formed  by  the  male-parent,  and  not 
by  the  mother,  as  one  parent  has  the  power  to  produce  it. 

Tills  idea  of  the  re-produeffion  of  animals  from  a lingle  liv- 
ing filament  of  their  fathers,  appears  to  have  been  fhadpwed 
or  allegorized  in  the  curious  account,  in  facred  writ,  of  die  for- 
mation of  Eve  from  a rib  of  Adam. 

From  all  thefe  analogies  I conclude,  that  the  embryon  is 
produced  folelv  by  the  male,  and  that  the  female  iupplies  it  with 
a proper  nidus,  with  fullenance,  and  with  oxygenation ; and 
diat  die  idea  of  the  femen  of  the  male,  conftituting  only  a fti- 
inulus  to  the  egg  of  the  female, exciting  it  into  life,  (as  held  by 
Tome  philofopbers)  has  no  fupport  from  experiment  or  analogy. 

III.  1.  Many  ingenious  pliilofophers  have  found  io  great 
difficulty  in  conceiving  the  manner  of  the  re-produ£tion  of  ani- 
mals, that  they  have  fuppofed  all  the  numerous  progeny  to 
have  exified  in  miniature  in  the  animal  originally  created;  and 
that  thefe  infinitely  minute  forms  are  only  evolved  or  diftend- 
ed,  as  the  embryon  increafes  in  the  womb.  This  idea,  heiides 
its  being  unfupported  by  any  analogy  we  are  acquainted  with, 
aferibes  a greater  tenuity  to  organized  matter  than  we  can 
readily  admit;  as  thefe  included  embryons  are  fuppofed  each 
of  them  to  conlift  of  the  various  and  complicate  parts  of  ani- 
mal bodies:  they  muff  poffefs  a much  greater  degree  of  mi- 
nutenefs,  than  that  which  was  aferibed  to  the  devils  that  tempt- 
ed St.  Anthony ; of  whom  20,000  were  faid  to  have  been  able 
to  dance  a faraband  on  the  point  of  the  fineit  needle  without 
incommoding  each  other. 

O 


2.  Others 


Sect.  XXXIX.  3-  OF  GENERATION1.  36* 

2.  Others  have  fuppofed,  that  all  the  parts  of  the  embryon 
are  formed  in  the  male,  previous  to  its  being  depofited  in  the 
egg  or  uterus ; and  that  it  is  then  only  to  have  its  parts  evolv- 
ed or  diftended,  as  mentioned  above;  but  this  is  only  to  get  rid 
of  one  difficulty  by  propofmg  another  equally  incomprehenft- 
ble  : they  found  it  difficult  to  conceive,  how  the  embryon  could 
be  formed  in  the  uterus  or  egg,  and  therefore  wifhed  it  to 
be  formed  before  it  came  thither.  In  anfvver  to  both  thefe  doc- 
trines it  may  be  obferved,  1 ft,  that  fome  animals,  as  the  crab- 
fifh,  can  re-produce  a whole  limb,  as  a leg  which  has  been 
broken  off ; others,  as  worms  and  (nails,  can  re-produce  a head, 
or  a tail, when  either  of  them  has  been  cut  away ; and  that  hence, 
in  thefe  animals,  at  lead  a part  can  be  formed  anew,  which 
eannot  be  fuppofed  to  have  exifted  previoufly  in  miniature. 

Secondly,  there  are  new  parts,  or  new  veffels,  produced  in 
many  difeafes,  as  on  the  cornea  of  the  eye  in  ophthalmy,  in 
wens  and  cancers,  which  cannot  be  fuppofed  to  have  had  a 
prototype  or  original  miniature  in  the  embryon. 

Thirdly,  how  could  mule-animals  be  produced,  which  par- 
take of  the  forms  of  both  the  parents,  if  the  original  embryon 
was  a miniature  exifting  in  the  femen  of  the  male  parent  ? If 
an  embryon  of  the  male  afs  was  only  expanded,  no  refen> 
blance  to  the  mare  could  exift  in  the  mule. 

This  miftaken  idea  ot  the  extenfion  of  parts  feerns  to  have 
had  its  rife  from  the  mature  man,  refembling  the  general  form 
of  the  foetus ; and  from  thence  it  was  believed,  that  the  parts 
of  the  feetus  were  diftended  into  the  man  ; whereas  they  have 
increafed  100  times  in  weight,  as  well  as  100  times  in  fize: 
now,  no  one  will  call  the  additional  99  parts  a diftention  of  the 
original  one  part  in  refpe6f  to  weight.  Thus,  the  uterus,  dur- 
ing pregnancy,  is  greatly  enlarged  in  thicknefs  and  folidity,  as 
well  as  in  capacity,  and  hence  rauft  have  acquired  this  addi- 
tional fize  by  accretion  of  new  parts,  not  by  an  extenfion  of 
the  old  ones : the  familiar  add  of  blowing  up  the  bladder  of  an 
animal  recently  flaughtered,  has  led  our  imaginations  to  apply 
this  idea  of  diftention  to  the  increafe  of  fize  from  natural 
growth;  which,  however,  muft  be  owing  to  the  apportion  of 
new  parts  ; as  it  is  evinced,  from  the  increafe  of  weight,  along 
with  the  increafe  or  dimenfion,  and  is  even  viftble  to  our  eyes, 
in  the  elongation  of  our  hair,  from  the  colour  of  its  ends  ; or, 
when  it  has  been  dyed  on  the  head  ; and  in  the  growth  of  our 
nails,  from  the  fpecks  fometimes  obfervable  on  them ; and  in 
the  increafe  of  the  white  crefcent  at  their  roots  ; and  in  the 
growth  of  new  flefh  in  wounds,  which  confifts  of  new  nerves 
as  well  as  of  new  blood- v'effels.. 


3.  Laftly, 


OF  GENERATION.  Sect.  XXXIX.  4. 

3.  Laftly,  Mr.  Bufron  has,  widr  great  ingenuity,  imagined 
the  exigence  of  certain  organic  particles,  which  are  fuppofed 
to  be  partly  alive,  and  partly  mechanic  fprings.  The  latter 
of  thefe  were  difcovered  by  Mr.  Needham,  in  the  milt  or  male 
organ  of  a fpecies  of  cuttle-fifh,  called  calmar;  the  former,  or 
living  animalcula,  are  found  in  bodr  male  and  female  fecretions, 
in  the  infufions  ot  feeds,  as  of  pepper,  in  the  jelly  of  roafted 
veal,  and  in  all  other  animal  and  vegetable  fubftances.  Thefe 
organic  particles  he  fuppofes  to  exift  in  the  fpermatic  fluids  of 
both  fexes,  and  that  they  are  derived  thither  from  every  part  of 
the  body,  and  muft  therefore  refemble,  as  he  fuppofes,  the  parts 
from  whence  they  are  derived.  Thefe  organic  particles  he  be- 
lieves to  be  in  conftanr  activity,  till  they  become  mixed  id  the 
womb,  and  then  they  inftantly  join  and  produce  an  embryon, 
or  foetus,  fimilar  to  the  two  parents. 

Many  objections  might  be  adduced  to  this  fanciful  theory  ; I 
fliall  only  mention  two : Fir  ft,  that  it  is  analogous  to  no  known 
animal  laws:  And,  fecondly,  that,  as  thefe  fluids,  replete  with 
organic  panicles,  derived  both  trom  the  male  and  remale  organs, 
are  fuppofed  to  be  fimilar,  there  is  no  reafon  why  the  momer 
fhould  not  produce  a female  embryon  without  the  affiltanceof 
the  male,  and  realize  the  lucina  fine  concubitu. 

IV.  1.  I conceive  the  primordium,  or  rudiment  of  die  em- 
bryon, as  fecreted  from  the  blood  of  the  parent,  to  con  if,  of  a 
Ample  living  filament,  as  a mufcular  fibre,  which  I fuppofe  to 
be  an  extremity  of  a nerve  of  locomotion,  as  a tib'-e  or  the  re- 
tina is  an  extremity  of  a nerve  of  fenfation ; as,  for  inftance, 
one  of  the  fibrils  which  compofe  the  mouth  of  an  ablorbent  vef- 
fel:  I fuppofe  this  living  filament,  of  whatever  form  it  may  be, 
whether  fphere,cube,  or  cylinder,  to  be  endued  with  the  capa- 
bility of  being  excited  into  aifiion  by  certain  kinds  of  ftimulus. 
By  the  ftimulus  ot  the  furrounding  fluid,  in  which  it  is  received 
from  the  male,  it  may  bend  into  a ring,  and  thus  form  the  be- 
ginning of  a tube.  Such  moving  filaments,  and  fuch  rings,  are 
deferibed  by  thole  who  have  attended  to  microicopic  animalcula^ 
This  living  ring  may  now  embrace  or  ablorb  a nutritive  particle 
of  the  fluid  in  which  it  fwims,  and,  by  drawing  it  into  its  pores,- 
or  joining  it,  by  compreffion,  to  its  extremities,  may  increaieits 
ovyn  length  or  craffitude;  and,  by  degrees,  tlie  living  ring  may 
become  a living  tube. 

2.  With  this  new  organization,  or  accretion  of  parts,  new 
kinds  ot  irritability  may  commence;  for  lo  long  as  there  was 
but  one  living  organ,  it  could  only  be  fuppofed  to  poflt-is  rriia- 
bility ; iinee  fenlibility  may  be  conceived  to  be  an  exceahon  c t 
the  effect  of  irritability  ever  the  reft  of  the  iyflem.  I hele  new 

• kinds 


3$3 


Sect.  XXXIX. 4.  OF  GENERATION. 

kinds  of  irritability  and  of  fenfibility  in  confequence  of  new  or- 
ganization, appear  from  variety  of  faffs  in  the  more  mature 
animal ; thus  the  formation  of  the  tefles,  and  confequent  fe- 
cretion  of  the  femen,  occafion  the  paffion  of  iuft ; the  lungs 
muft  be  previoufly  formed  before  their  exertions  to  obtain  frefii 
air  can  exift  ; the  throat  or  cefophagus  muft  be  formed  previ- 
ous to  the  fenfation  or  appetites  of  hunger  and  thirft ; one  of 
which  feems  to  refide  at  the  upper  end,  and  the  other  at  the  lower 
end  of  that  canal. 

Thus  alfo  the  glans  penis,  when  it  is  diftended  with  blood, 
acquires  a new  fenfibility,  and  a new  appetency.  The  fame 
occurs  to  the  nipples  of  the  breafts  of  female  animals  ; when  they 
are  diftended  with  blood,  they  acquire  the  new  appetency  of  giv- 
ing milk.  So  inflamed  tendons  and  membranes,  and  even  bones, 
acquire  new  fenfations ; and  the  parts  of  mutilated  animals,  as 
of  wounded  fnails,  and  polypi,  and  crabs,  are  re-produced  ; and 
at  the  fame  time  acquire  fenfations  adapted  to  their  lituations. 
Thus,  when  the  head  of  a fnail  is  re-produced  after  decollation, 
with  a fharp  razor,  thofe  curious  telefcopic  eyes  are  alfo  re-pro- 
duced, and  acquire  their  fenfibility  to  light,  as  well  as  their 
adapted  mufcles  for  retraction  on  the  approach  of  injury. 

With  every  new  change,  therefore,  of  organic  form,  or  ad- 
dition of  organic  parts,  I fuppofe  a new  kind  ot  irritability  or  of 
fenfibility  to  be  produced  ; iuch  varieties  of  irritability  or  of  fen- 
fibility exift  in  our  adult  ftate  in  the  glands  ; every  one  of  which 
is  furnifhed  with  an  irritability,  or  a tafte,  or  appetency,  and  a 
confequent  mode  of  aCtion  peculiar  to  itfelf. 

I11  this  manner  I conceive  the  veifels  of  the  jaws  to  produce 
thofe  of  the  teeth,  thofe  of  the  fingers  to  produce  the  nails,  thofe 
of  the  fkin  to  produce  the  hair  ; in  the  lame  manner  as  after- 
wards, about  the  age  of  puberty  the  beard  and  other  great  changes 
in  the  form  of  the  body,  and  difpofition  of  the  mind,  are  pro- 
■ duced  in  confequence  of  the  new  fecretion  of  femen  ; for  if  the 
animal  is  deprived  of  this  fecretion,  thofe  changes  do  not  take 
place.  Thefe  changes  I conceive  to  be  formed  not  by  elonga- 
tion or  diftention  of  primeval  ftamina,  but  by  appofition  off 
parts  ; as  the  mature  crab-fifh,  when  deprived  of  a limb,  in  a 
c ertain  fpace  of  time  has  power  to  regenerate  it  ; and  the  tad- 
pole puts  forth  its  feet  long  after  its  exclufion  from  the  fpawn  ; 
and  the  caterpillar,  in  changing  into  a butterfly,  acquires  a new 
form,  with  new  powers,  new  fenfations,  and  new  defires. 

The  natural  hiftory  of  butterflies,  and  moths,  and  beetles,  and 
gnats,  is  full  ot  curiofity  ; fome  of  them  pafs  many  months,  and 
others  even  years,  in  their  caterpillar  or  grub  ftate;  they  then 
reft  many  weeks  without  food,  lufpended  in  the  air,  buried  in 

B b b the- 


364  OF  GENERATION.  Sect.  XXXIX.  4, 

the  earth,  or  fubmerfed  in  water ; and  change  themfelves,  dur- 
ing this  time,  into  an  animal  apparently  of  a different  nature  : 
the  ftomachs  of  fome  of  them,  which,  before,  digefted  vegetable 
leaves  or  roots,  now  only  digeft  honey ; they  have  acquired 
wings  for  the  purpofe  of  feeking  this  new  food,  and  a long  pro- 
bofcis  to  collect  it  from  flowers,  and,  I fuppofe,  the  fenle  of 
ftnell  to  detedl  the  fecret  places  in  flowers,  where  it  is  formed. 
The  moths,  which  fly  by  night,  have  a much  longer  probofffs 
rolled  up  under  their  chins  like  a watch  fpring,  which  they  ex- 
tend to  colled!  the  honey  from  flowers  in  their  fleeping  ftate, 
when  they  are  clofed,  and  the  nedlaries  in  confequence  more 
difficult  to  be  plundered.  The  beetle  kind  are  furnillied  with 
an  external  covering  of  a hard  material  to  their  wings,  that 
they  may  occaiionally  again  make  holes  in  the  earth,  in  which 
they  palTed  the  former  Hate  of  their  exiflence. 

But  what  mod.  of  all  diftinguilhes  thefe  new  animals  is, 
that  they  are  new  furnillied  with  the  powers  of  re-produdlion ; 
and  that  they  now  differ  from  each  other  in  lex,  which  does 
not  appear  in  their  caterpillar  or  grub  Hate.  In  fome  of  them, 
the  change  from  a caterpillar  into  a butterfly,  or  moth,  feems  to 
be  accomplilhed  for  the  foie  purpofe  of  their  propagation ; 
lince  they  immediately  die  after  this  is  finilhcd,  and  take  no 
food  in  the  interim,  as  the  filk-worm  in  this  climate ; though 
it  is  poflibie,  it  might  take  honey  as  food,  if  it  was  prefented 
to  it.  For,  in  general,  it  would  feem,  that  food  of  a more  fti- 
mulating  kind,  the  honey  of  vegetables,  inflead  of  their  leaves, 
was  necelfary  for  the  purpofe  of  the  feminal  re-production  of 
thefe  animals,  exadtly  fimilar  to  what  happens  in  vegetables 
in  thefe  the  juices  of  the  earth  are  fufficient  for  their  purpofe  of 
re-produdtion  by  buds  or  bulbs ; in  which  the  new  plant  feems 
to  be  formed  by  irritative  motions,  like  the  growth  of  their  other 
parts,  as  their  leaves  or  roots ; but,  for  the  purpofe  of  feminal 
or  amatorial  re-produdlion,  where  fenfation  is  required,  a more 
ftimulating  food  becomes  necelfary  for  the  anther,  and  ftigma , 
and  this  food  is  honey;  as  explained  in  Sedt.  XIII.  on  "Vege- 
table Animation. 

The  gnat  and  thetaupole  referable  each  other  in  their  change 
from  natant  animals,  with  gills,  into  aerial  animals  with  lungs, 
and  in  their  change  of  the  element  in  which  they  live,  and  pro- 
bably of  the  food  with  which  they  are  fupported ; and,  laftly, 
with  their  acquiring  in  their  new  ft  ate  the  difference  of  lex, 
and  the  organs  of  feminal  or  amatorial  re-produchon.  While 
the  polvpus,  who  is  their  companion  in  their  former  ftate  of 
life,  not  being  allowed  to  change  his  form  and  element,  can 
only  propagate,  like  vegetable  buds,  by  the  fame  kind  ol  irrita- 


•Sect. XXXIX. 4-  OF  GENERATION.  365 

five  motions  which  produces  the  growth  of  his  own  body, 
without  the  feminal  or  amatorial  propagation,  which  require 
fenfation ; and  which,  in  gnats  and  tadpoles,  feems  to  require 
a change  both  of  food  and  of  rcfpiration. 

From  hence  I conclude,  that,  with  the  acquifition  of  new 
parts,  new  fenfations,  and  new  defires,  as  well  as  new  powers, 
are  produced ; and  this  by  accretion  to  the  old  ones,  and  not  by 
diftention  of  them.  And,  finally,  that  the  mo  ft  eflential  parts 
■of  the  fyftem,  as  the  brain  for  the  purpofe  of  diftributing,  the 
power  of  life,  and  the  placenta  for  the  purpofe  of  oxygenating 
.the  blood,  and  the  additional  abforbent  veifels  for  the  purpofe 
of  acquiring  aliment,  are  firft  formed  by  the  irritations  above 
mentioned,  and  by  the  pleafureable  fenfations  attending  thofe 
■irritations,  and  by  the  exertions  in  conlequence  of  painful  fen- 
fations, fxmilar  to  thofe  of  hunger  and  fuffocation.  After  theffe 
an  apparatus  of  limbs  for  future  ufes,  or  for  the  purpofe  of 
:moving  the  body  in  its  prefent  natant  ftate,  and  of  lungs  for 
future  refpiration,  and  of  teftes  for  future  reproduction,  are 
Formed  by  the  irritations  and  fenfations,  and  confequent  exer- 
tions of  the  parts  previoufly  exiting,  and  to  which  the  new 
' parts  are  to  be  attached. 

3.  In  confirmation  of  thefe  ideas,  it  may  be  obferved,  that  all 
the  parts  of  the  body  endeavour  to  grow,  or  to  make  additional 
parts  to  themfelves,  throughout  our  lives,  but  are  reftrained  by 
the  parts  immediately  containing  them : thus,  if  the  fkin  be 
taken  away,  the  flefhy  parts  beneath  foon  firoot  out  new  gra- 
nulations, called  by  the  vulgar  proud  fiefh.  If  the  periofteum 
•fee  removed,  a fimilar  growth  commences  from  the  bone.  Now, 
in  the  cafe  of  the  imperfect  embryon,  the  containing  or  con- 
fining parts  are  not  yet  fuppofed  to  be  formed,  and  hence  there 
is  nothing  to  retrain  its  growth. 

4.  By  the  parts  of  the  embryon  being  thus  produced  by  new 
appofitions,  many  phenomena,  both  of  animal  and  vegetable 
productions,  receive  an  eafier  explanation  ; fuch  as  that  many 
foetufes  are  deficient  at  the  extremities,  as  in  a finger  or  a toe, 
or  in  the  end  of  the  tongue,  or  in  what  is  called  a hair-lip,  with 
deficiency  of  the  palate.  For,  if  there  fhould  be  a deficiency 
in  the  quantity  of  the  firft  nutritive  particles  laid  up  in  the  egg 
■for  the  reception  of  the  firft  living  filament,  the  extreme  parts, 
as  being  laft  formed,  muft  mew  this  deficiency,  by  their  being 
imperfect. 

This  idea  of  the  growth  of  the  embryon  accords  alfo  with 
the  production  of  fome  monftrous  births,  which  confift  of  a 
duplicature  of  the  limbs,  as  chickens  with  four  legs ; which 
could  not  occur,  if  the  fcetus  was  formed  by  the  diftention  of 


§66  OF  GENERATION.  Sect.  XXXIX.  4 

an  original  Teamen,  or  miniature.  For,  if  there  fhould  be  a 
fuperiority  of  the  firft  nutritive  particles  laid  up  in  the  egg  for 
the  firft  living  filament,  it  is  eafy  to  conceive,  that  a duplica- 
ture  of  fome  parts  may  be  formed.  And  that  fuch  fuperflu- 
ous  nourishment  fometimes  exifts,  is  evinced  by  the  double  voiles 
in  fome  eggs,  which  I fuppofe  were  thus  formed  previous  to 
their  impregnation  by  the  exuberant  nutriment  of  the  hen. 

This  idea  is  confirmed  by  the  analogy  of  the  monfters  in  the 
vegetable  world  alfo  ; in  which  a duplicate  or  triplicate  produc- 
tion of  various  parts  of  the  flower  is  obfervable,  as  a triple  nec- 
tary in  fome  columbines,  and  a triple  petal  in  fome  primrofes; 
and  which  are  fuppofed  to  be  produced  by  abundant  nouriih- 
ment. 

3.  If  the  embryon  be  received  into  a fluid,  whofe  ftimulus  is 
different,  in  fome  degree,  from  the  natural,  as  in  the  produc- 
tion of  mule-animals,  the  new  irritabilities  or  fenfibilities  ac- 
quired by  the  increafing  or  growing  organized  parts,  may  dif- 
fer, and  thence  produce  parts  notfimilar  to  the  father,  but  of  a 
kind  belonging,  in  part,  to  the  mother;  and  thus,  though  the 
original  ftameft,  or  living  ens,- was  derived  totally  from  the  fa- 
ther, yet  new  irritabilities  or  fenfibilities  being  excited,  a change 
of  form  correfponding  with  them  will  be  produced.  Nor  could 
the  production  of  mules  exift,  it  the  ftamen  or  miniature  of 
all  the  parts  of  the  embryon  is  previoufly  formed  in  the  male 
femen,  and  is  only  difiended  by  nourifhment  in  the  female  ute- 
rus. Whereas,  this  difficulty  ceafes,  if  the  embryon  be  fup- 
pofed to  confifr  of  a living  filament,  which  acquires  or  makes 
new  parts  with  new  irritabilities,  as  it  advances  in  its  growth. 

The  form,  folidity,  and  colour  of  the  particles  of  nutri- 
ment laid  up  for  the  reception  of  the  firft  living  filament,  as 
well  as  their  peculiar  kind  of  ftimulus,  may  contribute  to  pro- 
duce a difference  in  the  form,  folidity,  and  colour  of  the  foetus, 
fo  as  to  referable  the  mother,  as  It  advances  in  life.  This  alio 
may  efpecially  happen  during  the  firft  ftate  of  the  exiftence  of 
the  embryon,  before  it  has  acquired  organs,  which  can  change 
thefe  firft  nutritive  particles,  as  explained  in  No.  5.  2.  of  this 
Section.  And  as  thefe  nutritive  particles  are  fuppofed  to  be 
flmilar  to  thole  which  are  formed  for  her  own  nutrition,  it 
follows  that  the  foetus  fhould  fo  far  referable  the  mother. 

This  explains,  why  hereditary  difeafes  may  be  derived  either 
from  the  male  or  female  parent,  as  well  as  the  peculiar  form  of 
either  of  their  bodies.  Some  of  thefe  hereditary  difeafes  are 
fimpiy  owing  to  a deficient  aCfivity  of  a part  of  the  fyftem,  as 
of  the  abforbent  rebels,  which  open  into  the  cells  or  cavities  of 
|'he  body,  and  thus  cccafion  droplies.  Others  are,  at  the  fame 


<Sect.XXXIX.4-  OF  GENERATION.  367 

.time,  owing  to  an  increafe  of  fenfation,  as  in  fcrophula  and 
.confumption : in  thefe  the  obftrudtion  of  the  fluids  is  firft  caufed 
by  the  inirritability  of  the  veflels ; and  the  inflammation  and 
ulcers  which  fucceed,  are  caufed  by  the  confequent  increafe  of 
fenfation  in  the  obft ruffed  part.  Other  hereditary  difeafes,  as 
the  epilepfy,  and  other  convulfions,  conflft  in  too  great  volun- 
tary exertions,  in  confequence  of  difagreeable  fenfation  in  fome 
particular  difeafed  part.  Now,  as  the  pains  which  occaflon 
thefe  convulfions  are  owing  to  defeff  of  the  aftion  of  the  dif- 
eafed part,  as  fhewn  in  Seff.  XXXIV.  it  is  plain,  that  all  thefe 
hereditary  difeafes  may  have  their  origin  either  from  defeffive 
irritability,  derived  from  the  father,  or  from  deficiency  of  the 
ftimulus  of  the  nutriment  derived  from  the  mother,  in  either 
cafe  die  effect  would  be  fimilar;  as  a fcrophulous  race  is  fre- 
quently produced  among  the  poor  from  the  deficient  ftimulus  of 
bad  diet,  or  of  hunger;  and  among  the  rich,  by  a deficient  irri- 
tability, from  their  having  been  long  accuftomed  to  too  great 
ftimulus,  as  of  vinous  fpirit.  / 

6.  From  this  account  of  re-produ6ti.on  it  appears,  that  all 
animals  have  a fimilar  origin,  viz.  from  a Angle  living  filament ; 
.and  that  the  difference  of  their  forms  and  qualities  has  arifen 
only  from  the  different  irritabilities  and  fenfibilities,  or  volunta- 
rities,  or  affociabilities,  of  this  original  living  filament,  and,  per- 
haps, in  fome  degree,  from  the  different  forms  of  the  particles 
of  the  fluids  by  which  it  has  been  at  firft  ftimu'iated  into  activity. 
And  that  from  hence,  as  Linnaeus  has  conjectured  in  refpedt  to 
the  vegetable  world,  it  is  not  impoflible  but  the  great  variety  of 
fpecies  of  animals  which  now  tenant  the  earth,  may  have  had 
their  origin  from  the  mixture  of  a few  natural  orders : and  that 
t’nofe  animals  and  vegetable  mules  which  could  continue  their 
fpecies,  have  done  fo,  and  conftitute  the  numerous  families  of 
animals  and  vegetables  which  now  exift ; and  that  thofe  mules 
which  were  produced  with  imperfedt  organs  of  generation,  pe- 
rifhed  without  re-produdtion,  according  to  the  obfervation  of 
Ariftotle  ; and  are  the  animals  which  we  now  call  mules.  See 
Botanic  Garden,  Part  II.  Note  on  Dianthus. 

Such  a promifcuous  intercourfe  of  animals  is  faid  to  exift  at 
this  day,  in  New  South  Wales,  by  Captain  Hunter:  and  that 
not  only  amongft  the  quadrupeds  and  birds  of  different  kinds, 
but  even  amongft  the  fifti,  and,  as  he  believes,  amongft  the  ve- 
getables. He  fpeaks  of  an  animal  between  the  opoffum  and  the 
kangaroo,  from  the  fize  of  a fheep  to  that  of  a rat.  Many  fifti 
jeemed  to  partake  of  the  (hark ; fome  with  a fkait’s  head  and 
fhoulders,  and  the  hind  part  of  a {hark;  others  with  a fliark’s 
jhead,  and  the  body  of  a mullet ; and  fome  with  a fhark’s  head, 


36$  OF  GENERATION.  Sect.  XXXIX.  4. 

and  the  flat  body  of  a fling-ray.  Many  birds  partake  of  the 
parrot;  fome  have  the  head,  neck,  and  bill  of  a parrot,  with 
long  ftraight  feet  and  legs ; others  with  legs  and  feet  of  a parrot, 
with  head  and  neck  of  a fca-gull.  Voyage  to  South  Wales,  by 
Captain  John  Hunter,  p.  68. 

7.  All  animals,  therefore,  I contend,  have  a fimilar  caufe  of 
their  organization,  originating  from  a Angle  living  filament, 
endued,  indeed,  with  different  kinds  of  irritabilities  and  fenfibi- 
lities,  or  of  animal  appetencies,  which  exift  in  every  gland,  and 
in  every  moving  organ  of  the  body,  and  are  as  eflential  to  living 
organization,  as  chemical  affinities  are  to  certain  combinations 
of  inanimate  matter. 

If  I might  he  indulged  to  make  a finale  in  a philofophical 
work,  I fhould  fay,  that  the  animal  appetencies  are  not  only 
perhaps  lefs  numerous  originally  than  the  chemical  affinities, 
but  that,  like  thefe  latter,  they  change  with  every  new  combi- 
nation ; thus  vital  air  and  azote,  when  combined,  produce  ni- 
trous acid ; which  now  acquires  the  property  of  diffolving  iilver : 
fo,  with  every  new  additional  part  to  the  embryon,  as  of  the 
throat  or  lungs,  I fuppofe  a new  animal  appetency  to  be  pro- 
duced. 

In  this  early  formation  of  the  embryon  from  the  irritabilities, 
fenfibilities,  and  affociabilities,  and  confequent  appetencies,  the 
faculty  of  volition  can  fcarcely  be  fuppofed  to  have  had  its  birth. 
For  about  what  can  the  foetus  deliberate,  when  it  has  no  choice  of 
objedls  ? But  in  the  more  advanced  ftate  of  the  fcetus,  it  evident- 
ly poflfeffes  volition  ; as  it  frequently  changes  its  attitude,  though 
it  feems  to  fieep  the  greatefl:  part  of  its  time ; and  afterwards  the 
power  of  volition  contributes  to  change  or  alter  many  parts  of 
the  body  during  its  growth  to  manhood,  by  our  early  modes  of 
exertion  in  :he  various  departments  of  lite.  All  thei'e  faculties 
then  conftitute  the  vis  fabricatrix,  and  the  vis  confervatrix,  as 
well  as  the  vis  mcdicatrix  of  nature,  fo  much  fpoken  of,  but  fo 
little  underftood  by  philofopbers. 

8.  When  we  revolve  in  our  minds,  firft,  the  great  changes 
which  we  fee  naturally  producedi  n animals  after  their  nativity, 
as  in  the  production  of  the  butterfly  with  painted  wings  from  the 
crawling  caterpillar;  or  of  the  refpiring  frog  from  the  lubna- 
tant  tadpole ; from  the  feminine  boy  to  the  bearded  man,  and 
from  the  infant  girl  to  the  laclefcent  woman  ; both  which 
changes  may  be  prevented  by  certain  mutilations  of  tire  glands 
necelfary  to  re-produfition. 

Secondly,  when  we  think  over  the  great  changes  introduced 
into  various  animals  bv  artificial  or  accidental  cultivation,  as  in 
horfes,  which  we  have  excrcifed  for  the  different  purpoies  of 

ilrengch 


Sect.  XXXIX. 4.  OF  GENERATION.  369 

ftrength  or  fwiftnefs,  in  carrying  burthens,  or  in  running  races ; 
or  in  dogs,  which  have  been  cultivated  for  ftrength  and  cou- 
rage, as  the  bull-dogs  ; or  for  acutenefs  of  his  fenfe  of  ftnell,  as 
the  hound  and  fpaniel ; or  for  the  fwiftnefs  of  his  foot,  as  the 
greyhound  ; or  for  his  fwitnming  in  the  water,  or  for  drawing 
'fnow  fledges,  as  the  rough-haired  dogs  of  the  north ; or  l'aftly, 
as  a play-dog  for  children,  as  the  lap-dog ; with  the  changes  of 
the  forms  of  the  cattle,  which  have  been  domefticated  from  the 
greateft  antiquity,  as  camels,  and  fheep,  which  have  undergone' 
fo  total  a transformation,  that  we  are  now  ignorant  from  what 
fpecies  of  wild  animals  they  had  their  origin.  Add  to  thefe  the 
great  changes  of  fhape  and  colour  which  we  daily  fee  produced 
in  fmaller  animals  from  our  domeftication  of  them,  as  rabits, 
or  pidgeons ; or  from  the  difference  of  climates  and  even  of  fea-- 
fons  ; thus  the  fheep  of  warm  climates  are  covered  with  hair 
inftead  of  wool ; and  the  hares  and  partridges  of  the  latitudes-' 
which  are  long  buried  in  fnow,  become  white  during  the  win- 
ter months  : add  to  thefe  the  various  changes  produced  in  the 
forms  of  mankind,  by  their  early  modes  of  exertion  ; or  by  the 
difeafes,  occafioned  by  their  habits  of  life;  both  of  which  be- 
came hereditary,  and  that  through  many  generations.  Thofe 
who  labour  at  the  anvil,  the  oar,  or  the  loom,  as  wrell  as  thofe 
who  carry  fedan-chairs,  or  who  have  been  educated  to  dance 
upon  the  rope,  are  diftinguifhable  by  the  fhape  of  their  limbs  ; 
and  the  difeafes  occafioned  by  intoxication  deform  the  counte- 
nance with  leprous  eruptions,  or  the  body  with  tumid  vifeera,. 
or  the  joints  with  knots  and  diftortions. 

Thirdly,  when  we  enumerate  the  great  changes  produced  in 
the  fpecies  of  animals  before  their  nativity : thefe  are  fuch  as  re- 
ferable the  term  or  colour  of  their  parents,  which  have  been 
altered  bv  the  cultivation  or  accidents  above  related,  and  are 
thus  continued  to  their  pofterity.  Or  they  are  changes  pro- 
duced by  the  mixture  ot  fpecies,  as  in  mules ; or  changes  pro- 
duced probably  by  the  exuberance  of  nourifhment  fupplied  to 
the  foetus,  as  in  monftrous  births  with  additional  limbs : many 
of  thefe  enormities  of  fhape  are  propagated,  and  continued  as 
a variety  at  leaft,  if  not  as  a new  fpecies  of  animal.  I have 
feen  a breed  of  cats  with  an  additional  claw  on  every  foot;  of 
poultry  all’o,  with  an  additional  claw,  and  with  wings  to  their 
feet ; and  of  others  without  rumps.  Mr.  BufFon  mentions  a 
breed  of  dogs  wtihout  tails,  which  are  common  at  Rome  and 
at  Naples,  which  he  fuppofes  to  have  been  produced  by  a cuf- 
tom,  long  eftablifhed,  of  cutting  their  tails  clofe  off.  There  are 
many  kinds  of  pigeons,  admired  for  their  peculiarities,  which 
are  monfters  thus  produced  and  propagated.  And  to  thefe  muft 

be- 


370  OF  GENERATION.  Sect.  XXXIX.  L 

be  added  the  changes  produced  by  the  imagination  of  the  male 
parent,  as  will  be  treated  of  more  at  large  in  No.  6.  of  this  Seft. 

When  we  confider  all  thefe  changes  of  animal  form,  and 
innumerable  others  which  may  be  colledled  from  the  books  of 
natural  hiftory,  we  cannot  but  be  convinced,  that  the  foetus,  or 
embryon,  is  formed  by  apportion  of  new  parts,  and  not  by  the 
diftention  of  a primordial  neil  of  germs,  included  one  within 
another,  like  the  cups  of  a conjurer. 

Fourthly,  when  we  revolve  in  our  minds  the  great  fimilarity 
of  ftructure  which  obtains  in  all  the  warm  blooded  animals, 
as  well  quadrupeds,  birds,  and  amphibious  animals,  as  in  man- 
kind ; from  the  moufe  and  bat,  to  the  elephant  and  w hale ; one 
is  led  to  conclude,  that  they  have  alike  been  produced  from  a 
fnnilar  living  filament.  In  fome,  this  filament,  in  its  advance 
to  maturity,  has  acquired  hands  and  fingers,  with  a fine  lenle 
of  touch,  as  in  mankind  : in  others  it  has  acquired  daws  or  ta- 
lons, as  in  tygers  and  eagles:  in  others,  toes,  with  an  interven- 
ing web,  or  membrane,  as  in  feals  and  gee'e  : in  others  it  has 
acquired  cloven  hoofs,  as  in  cows  and  fwine ; and  whole  hoofs 
in  others,  as  in  the  horfe.  While,  in  the  bird  kind,  this  original 
living  filament  has  put  forth  wings  inftead  of  arms  or  legs,  and 
feathers  inftead  of  hair.  In  fome  it  has  protruded  horns  on  the 
forehead,  inftead  of  teeth  in  the  fore  part  of  the  upper  jaw : in 
others,  tufnes  inftead  of  horns ; and  in  others,  beaks  inftead 
of  either.  And  all  this  exadtlv  as  is  daily  feen  in  the  tranfmu- 
tations  of  the  tadpole,  winch  acquires  legs  and  lungs  when  he 
wants  them,  and  lofes  his  tail  when  it  is  no  longer  of  fen-ice-' 
to  him. 

Fifthly,  from  their  firft  rudiment,  or  primordium,  to  the  ter- 
mination of  their  lives,  all  animals  undergo  perpetual  transfor- 
mations, which  are,  in  part,  produced  by  their  ow  n exertions,  in 
confequence  of  their  defil  es  and  averfions,  of  their  pieaiures  and 
their  pains ; or  of  irritations,  or  of  affociations ; and  many  of 
thefe  acquired  forms  or  propeniities  are  tranimitted  to  their 
pofterity.  See  Se£t.  XXXI.  1. 

As  air  and  wrater  are  fupplied  to  animals  in  fufficient  profu- 
fion,  the  three  great  objedfs  of  defire,  which  have  changed  the 
forms  of  many  animals  by  their  exertions  to  gratify  them,  are 
thole  of  luff,  hunger,  and  fecuritv.  A great  want  of  one  part 
of  the  animal  world  has  confided  in  the  deiire  of  the  exclulive 
poffeffion  of  the  females  ; and  thefe  have  acquired  weapons  to 
combat  each  other  for  this  purpofe,  as  the  very  thick,  fhield- 
like,  horny  fkin  on  the  fhoulder  of  the  boar,  is  a defence  only 
againft  animals  of  his  own  fpecies,  who  ftrike  obliquely  up- 
wards ; nor  are  his  tufhes  for  other  purpoies,  except  to  defend 

hiinfelf. 


Sect.  XXXIX.  4.  OF  GENERATION.  37 .i 

himfelf,  as  he  is  not  naturally  a carnivorous  animal.  So  the 
horns  of  the  flag  are  fharp,  to  offend  his  adverfary;  but  are 
branched,  for  the  purpofe  of  parrying  or  receiving  the  thrufts 
of  horns  fimrlar  to  his  own,  and  have  therefore  been  formed 
for  the  purpofe  of  combating  other  flags  for  the  exclufive  pof- 
feffion  of  the  females,  who  are  obferved,  like  the  ladies  in  the 
times  of  chivalry,  to  attend  the  car  of  the  viddor. 

The  birds  which  do  not  carry  food  to  their  young,  and  do' 
not  therefore  marry,  are  armed  with  fpurs  for  the  purpofe  of 
fighting  for  the  exclufive  poffeflion  of  the  females,  as  cocks 
and  quails.  It  is  certain,  that  thefe  weapons  are  not  provided 
for  their  defence  againft  other  adverfaries,  becaufe  the  females 
of  thefe  fpecies  are  without  this  armour.  The  final  caufe  of 
this  conteft  amongft  the  males  feems  to  be,  that  the  ftrongeft 
and  moft  addive  animal  fhould  propagate  the  fpecies,  which 
fhould  thence  become  improved. 

Another  great  want  conlifts  in  the  means  of  procuring  food, 
which  has  diverfified  the  forms  of  all  fpecies  of  animals.  Thus, 
the  nofe  of  the  fwine  has  become  hard,  for  the  purpofe  of  turn- 
ing up  the  foil  in  fearch  of  infedds  and  of  roots.  The  trunk  of 
the  elephant  is  an  elongation  of  the  nole,  for  the  purpofe  of 
pulling  down  the  branches  of  trees  for  his  food,  and  for  taking 
up  water  without  bending  his  knees.  Beafts  of  prey  have  ac- 
quired ftrong  jaws  or  talons.  Catde  have  acquired  a rough- 
tongue  and  a rough  palate,  to  pull  off  the  blades  of  grafs,  as 
cows  and  fheep.  Some  birds  have  acquired  harder  beaks  to 
crack  nuts,  as  the  parrot  : others  have  acquired  beaks  adapted 
to  break  the  harder  feed's,  as  fparrows : others,  for  the  fofter 
feeds  of  flowers,  or  the  buds  of  trees,  as  the  finches:  other 
birds  have  acquired  long  beaks,  to  penetrate  the  moifter  foils  in 
fearch  of  infeeds  or  roots,  as  woodcocks ; and  others,  broad 
ones,  to  filtrate  the  water  of  lakes,  and  to  retain  aquatic  infedds. 
All  which  feem  to  have  been  gradually  produced,  during  many 
generations,  by  the  perpetual  endeavour  of  the  creatures  to  fupply 
the  want  of  food,  and  to  have  been  delivered  to  their  pofterity, 
with  conftant  improvement  of  them,  for  the  purpofes  required. 

The  third  great  want  amongft  animals  is  that  of  iecurity, 
which  feems  much  to  have  diverfified  the  forms  of  their  bodies, 
and  the  colour  of  them  : thefe  confift  in  the  means  of  efcaping 
other  animals  more  powerful  than  themfelves.  Hence  fome 
animals  have  acquired  wings  inftead  of  legs,  as  the  fmaller 
birds,  for  the  purpofe  of  efcape : others,  great  length  of  fin,  or 
ot  membrane,  as  the  fiying-firh  and  the  bat : others,  great  fwi fi- 
nds ot  foot,  as  the  hare:  others  have  acquired  hard  or  armed 
fhells,  as  the  tortoife  and  the  echinus  marinus. 

C c c 


The 


572  OF  GENERATION".  Sect.  XXXIX.  £ 

The  contrivances  for  the  purpofes  of  feourity  extend  even  to 
vegetables,  as  is  feen  in  the  wonderful  and  various  means  of  their 
concealing  or  defending  their  honey  from  infedds,  and  their  feeds 
from  birds.  On  the  other  hand,  fwiftnefs  of  wing  has  been  ac- 
quired by  hawks  and  iwallows,  to  purfue  their  prey;  and  a 
probofcis,  of  admirable  ftruFture,  has  been  acquired  by  the  bee, 
the  moth,  and  the  humming-bird,  for  the  purpofe  of  plundering 
the  nedtaries  of  flowers.  All  which  feem  to  have  been  formed 
by  the  original  living  filament,  excited  into  aclion  by  the  necef- 
fities  of  the  creatures  which  poflfels  them,  and  on  which  their 
exiftence  depends. 

From  thus  meditating  on  the  great  fimilarity  of  the  ftrudfure 
of  the  warm-blooded  animals,  and,  at  tire  fame  time,  of  the  great 
changes  they  undergo,  both  before  and  after  their  nativity,  and 
by  confidering  in  how  minute  a portion  of  time  many  of  the 
changes  of  animals  above  deferibed  have  been  produced  ; would 
it  be  too  bold  to  imagine,  that,  in  the  great  length  of  time  fince 
the  earth  began  to  exift,  perhaps  millions  of  ages  before  the 
commencement  of  the  hiftory  of  mankind, — would  it  be  too 
bold  to  imagine,  that  all  warm-blooded  animals  have  arifen 
from  one  living  filament,  which  the  great  First  Cause 
endued  with  animality,  with  the  power  of  acquiring  new'  parts, 
attended  with  new  propenfities,  directed  by  irritations,  fenfations, 
volitions,  and  aflbeiations ; and  thus  poffeffing  the  faculty  of 
continuing  to  improve  by  its  own  inherent  adlivity,  and  or  de- 
livering dow  n thofe  improvements,  by  generation,  to  its  pofte- 
rity,  world  without  end  ! 

Sixthly,  The  cold-blooJed  animals,  as  the  fifh  tribes,  which 
are  furniihed  with  but  one  ventricle  of  the  heart,  and  with  gills 
inflead  of  lungs,  and  with  fins  inftead  of  feet  or  wings,  bear  a 
great  fimilarity  to  each  other;  but  they  ditfer,  neverthelefs,  lo 
much  in  their  general  ftrudture  from  the  warm-blooded  animals, 
that  it  may  not  feem  probable,  at  firft  view,  that  the  fame  living 
filament  could  have  given  origin  to  this  kingdom  of  animals, 
as  to  the  former.  Yet  are  there  fome  creatures,  which  unite 
or  partake  of  both  thele  orders  of  animation,  as  the  whales  and 
feals  ; and  more  particularly  the  frog,  who  changes  from  an 
aquatic  animal  furniflred  with  gills,  to  an  aerial  one  fur  mined 
with  lufigs. 

The  numerous  tribes  of  infedts  without  wings,  from  thefpi- 
der  to  thefcorpion,  from  the  flea  to  the  lobfler ; or  with  wings, 
from  the  gnat  and  the  ant  to  the  wafp  and  the  dragon-flv,  dif- 
fer fo  totally  from  each  ocher,  aud  from  the  red-blooded  daffies 
above  delcribed,  both  in  the  forms  of  their  bodies,  and  their 
modes  of  life ; belides  the  organ  of  fenfe  which  they  feem  to  pofi- 

fefs 


'Sect. XXXIX.  4-  OF  GENERATION.  573 

fefs  in  their  antenna;  or  horns,  to  which  it  has  been  thought  by 
fome  naturalifts,  that  other  creatures  have  nothing  Similar ; that 
-it  can  fcarcely  be  fuppofed  that  this  nation  of  animals  could 
have  been  produced  bv  the  fame  kind  of  living  filament,  as  the 
.red-blooded  claffes  above  mentioned.  And  yet  the  changes 
which  many  of  them  undergo  in  their  early  ftate  to  that  of  their 
maturity,  are  as  different  as  one  animal  can  be  from  another : as 
thofe  of  the  gnat,  which  paffes  his  early  ftate  in  water,  and 
then  ftretching  out  his  new  wings,  and  expanding  his  new  lungs, 
rifes  in  the  air;  as  of  the  caterpillar,  and  bee-nymph,  which 
feed  on  vegetable  leaves,  or  farina,  and  at  length,  burfting  from 
their  felf-formed  graves,  become  beautiful  winged  inhabitants 
of  the  {kies,  journeying  from  flower  to  flower,  and  nourifhed 
■by  the  ambrofial  food  of  honey. 

There  is  ftill  another  clafs  of  animals,  which  are  termed  ver- 
mes by  Linnaeus,  which  are  without  feet,  or  brain,  and  are 
hermaphrodites,  as  worms,  leeches,  inails,  fhell-fifh,  coralline 
infefts,  and  fponges;  which  poffefs  the  fimplefl  ftrudture  of  all 
animals,  and  appear  totally  different  from  thofe  already  defer ib- 
ed.  The  fimplicity  of  their  ftrudlure,  however,  can  afford 
no  argument  againft  their  having  been  .produced  .from  a living- 
filament  as  above  contended. 

Laft  of  all,  the  various  tribes  of  vegetables  are  to  be  enume- 
rated amongft  the  inferior  orders  of  animals.  Of  thefe  the  an- 
thers and  ftigmas  have  already  been  fhewn  to  poffefs  fome  or- 
gans of  fenfe,  to  be  nourifhed  by  honey,  and  to  have  the  power 
of  generation  like  infedls,  and  have  thence  been  announced 
amongft  the  animal  kingdom  in  Seel.  XIII.  and  to  thefe  muft 
«be  added  the  buds  and  bulbs  which  conftitute  the  viviparous  off- 
-fpring  of  vegetation.  The  former  I fuppofe  to  be  beholden  to 
a fingle  living  filament  for*  their  feminal  or  amatorial  procrea- 
tion ; and  the  latter  to  the  fame  caufe  for  their  lateral  or  branch- 
ing generation,  which  they  poffefs  in  common  with  the  poly- 
pus, tenia,  and  volvox ; and  the  fimplicity  of  which  is  an  ar- 
gument in  favour  of  the  fimilarity  of  its  caufe. 

Linnasusfuppofes,  in  the  Introduction  to  his  Natural  Orders, 
that  very  few  vegetables  were  at  firft  created,  and  that  their 
numbers  were  increafed  by  their  intermarriages,  and  adds,  fua- 
dent  hasc  Creatoris  leges  a limplicibus  ad  compofita.  Many 
other  changes  feem  to  have  ariien  in  them  by  their  perpetual 
conteft  for  light  and  air  above  ground,  and  for  food  or  moif- 
-ture  beneath  the  foil:  as  noted  in  Botanic  Garden,  Part  II. 
Note  on  Cufcuta.  Other  changes  of  vegetables  from  climate, 
or  other  caules,  are  remarked  in  the  note  on  Curcuma  in  the 
djune  work.  From  thefe  one  might  be  led  to  imagine,  that  each 

plant 


f74  OF  GENERATION.  Sect.  XXXIX.  4. 

plant  at  firft  confifted  of  a Engle  bulb  or  flower  to  each  root, 
as  the  gentianella  and  daily;  and  that  in  theconteft  for  air  and 
light,  new  buds  grew  on  the  old  decaying  flower-ftem,  (hom- 
ing down  their  elongated  roots  to  the  ground : and  that  in  pro- 
cefs  of  ages,  tall  trees  were  thus  formed,  and  an  individual  bulb 
became  a fwarm  of  vegetables.  Other  plants,  which,  in  this 
conteft  for  light  and  air,  were  too  (lender  to  rife  by  their  own 
ftrength,  learned,  by  degrees,  to  adhere  to  their  neighbours,  ei- 
ther by  putting  forth  roots  like  the  ivy,  or  by  tendrils  like  the 
vine,  or  by  fpiral  contortions  like  the  honey-fuckle ; or  by 
growing  upon  them  like  the  mifleto,  and  taking  nourifhment 
from  their  barks ; or  by  only  lodging  or  adhering  on  them,  and 
deriving  nourifhment  from  the  air,  as  tiilandfia. 

Shall  we  then  fay,  that  the  vegetable  living  hlament  was  ori- 
ginally different  from  that  of  each  tribe  of  animais  above  de- 
feribed?.  And  that  the  productive  living  filament  of  each  of 
thofe  tribes  was  different  originally  from  the  other  r Or,  as  the 
earth  and  ocean  were  probably  peopled  with  vegetable  produc- 
tions long  before  the  exiflence  of  animals,  and  manv  families 
of  thefe  animals  long  before  other  families  of  them,  fhaii  we 
conjecture,  that  one  and  the  fame  kind  of  living  Elements  is, 
and  has  been  the  caufe  of  all  organtic  iife  ? 

This  idea  of  the  gradual  formation  and  improvement  of  tire 
animal  world,  accords  with  the  obfervations  of  fome  modern 
philofophers,  who  have  fuppofed,  that  the  continent  of  Ame- 
1 ica  has  been  railed  out  of  the  ocean  at  a later  period  of  time 
than  the  other  three  quarters  of  the  globe,  which  they  deduce 
from  the  greater  comparative  heights  of  its  mountains,  and  the 
confequent  greater  coldnefs  of  its  rei'pedtive  climates,  and  from 
the  iefs  lize  and  ftrength  of  its  animals,  as  the  tygers  and  alle- 
gators,  compared  with  thofe  of  Ala  or  Africa.  And  laitiv, 
from  the  lefs  progrefs  in  the  improvements  of  tire  mind  of  its 
inhabitants  in  refpedt  to  voluntary  exertions. 

This  idea  of  the  gradual  formation  and  improvement  of  the 
animal  world,  feems  not  to  have  been  unknown  to  the  ancient 
philofophers.  Plato  having  probably  obferved  the  reciprocal 
generation  of  inferior  animals,  as  (nails  and  worms,  was  of 
opinion,  that  mankind,  with  all  other  animals,  were  originally 
hermaphrodites  during  the  infancy  of  the  world,  and  were,  in 
procefs  of  time,  (Separated  into  male  and  female.  The  breads 
and  teats  of  all  male  quadrupeds,  to  which  no  ufe  can  be  now 
aligned,  adds,  perhaps,  fome  fhadow  of  probability  to  this  opi- 
nion. Liunrous  excepts  the  horle  from  the  male  quadrupeds, 
who  have  teats ; which  might  have  (hewn  the  earlier  origin  of 
pis  exiiknee;  but  Mr.  T.  Hunter  aliens,,  that  he  has  diico- 

vered 


Sect.  XXXIX.  5.  OF  GENERATION.  375 

vered  the  veftiges  of  them  on  his  (heath,  and  has,  at  the  fame 
time,  enriched  natural  hiftory  with  a very  curious  fa£t  con- 
cerning the  male  pigeon  ; at  the  time  of  hatching  the  eggs, 
both  the  male  and  female  pigeon  undergo  a great  change  in 
their  crops,  which  thicken  and  become  corrugated,  and  fecrete 
a kind  of  milky  fluid,  which  coagulates,  and  with  which  alone 
they,  for  a few  days,  feed  their  young,  and  afterwards  feed  them 
with  this  coagulated  fluid  mixed  with  other  food.  How  this 
refembles  .the  breath  of  female  quadrupeds  after  the  produdtion 
of  their  young ! and  how  extraordinary  that  the  male  fliould 
at  this  time  give  milk  as  well  as  the  female  ! See  Botanic  Gar- 
den, Part  II,  Note  on  Curcuma. 

The  late  Mr,  David  Hume,  in  his  pofthumous  works,  places 
the  powers  of  generation  much  above  thofe  of  our  boafted  rea- 
fon  ; and  adds,  that  reafon  can  only  make  a machine,  as  a clock 
or  a thip,  but  the  power  of  generation  makes  the  maker  of  the 
machine;  and  probably  from  having  obferved,  that  the  greatelt 
part  of  the  earth  has  been  formed  out  of  organic  recrements ; 
as  the  immenfe  beds  of  limeftone,  chalk,  marble,  from  the  (hells 
of  flfh  ; and  the  extenflve  provinces  of  clay,  fandftone,  iron- 
ftone,  coals,  from  decompofed  vegetables ; all  which  have  been 
firfl:  produced  by  generation,  or  by  the  fecretions  of  organic 
life:  he  concludes,  that  the  world  itfelf  might  have  been  gene- 
rated rather  than  created;  that  is,  it  might  have  been  gradually 
produced  from  very  fmall  beginnings,  increaflng  by  the  adlivitv 
of  its  inherent  principles  rather  than  by  a fudden  evolution  of 
the  whole  by  the  Almighty  flat. — What  a magnificent  idea  of 
the  infinite  power  of  The  Great  Architect!  The 
.Cause  of  Causes  ! Parent  of  Parents!  Ens  En- 
tium  ! 

For  if  we  may  compare  infinities,  it  would  feem  to  require 
a greater  infinity  of  power  to  caufe  the  caufes  of  effects,  than 
to  caufe  the  effects  themfelves.  This  idea  is  analogous  to  the 
improving  excellence  obfervuble  in  every  part  of  the  creation; 
fuch  as  in  the  progreffive  increafe  of  the  folid  or  habitable  parts 
of  the  earth  from  water,  and  in  the  progreffive  increafe  of  the 
wifdom  and  happinefs  of  its  inhabitants ; and  is  confonant  to 
the  idea  of  our  prefect  fituation,  being  a ftate  of  probation, 
which,  by  our  exertions,  we  may  improve,  and  are  consequent- 
ly refponilble  for  our  actions. 

V.  1.  The  efficient  caufe  of  the  various  colours  of  the  eggs 
of  birds,  and  of  the  hair  and  feathers  of  animals,  is  a fubjedl 
fo  curious,  that  I fhall  beg  to  introduce  it  in  this  place.  The 
colours  of  many  animals  feem  adapted  to  their  purpofes  of  con- 
cealing themfelves  either  to  avoid  danger,  or  to  fpring  upon 

their 


376  OF  GENERATION.  Sect.XXXIX.^ 

their  prey.  Thus  the  fnake,  and  wild-cat,  and  leopard,  are  fo 
coloured  as  to  refemble  dark  leaves  and  their  lighter  interftices  , 
birds  refemble  the  colour  of  the  brown  ground,  or  the  green 
hedges  which  they  frequent ; and  moths  and  butterflies  are  co- 
loured like  the  flowers  which  they  rob  of  their  honey.  Many 
inftances  are  mentioned  of  this  kind  in  Botanic  Garden,  Part 
II.  Note  on  Rubia. 

Thefe  colours  have,  however,  in  fome  inftances,  another  ufe, 
as  the  black  diverging  area  from  the  eyes  of  the  fwan  ; which, 
as  his  eyes  are  placed  lefs  prominent  than  thofe  of  other  birds, 
for  the  convenience  ot  putting  down  his  head  under  water, 
prevents  the  rays  of  light  from  being  reflected  into  his  eye,  and 
thus  dazzling  his  fight,  both  in  air  and  beneath  the  water, 
which  muft  have  happened  if  that  furlace  had  been  white  like 
the  reft  of  his  feathers. 

There  is  a ftiil  more  wonderful  thing  concerning  thefe  co- 
lours, adapted  to  the  purpofe  of  concealment;  which  is,  that 
the  eggs  ot  birds  are  fo  coloured  as  to  refemble  the  colour  of  the 
adjacent  objects  and  their  interftices.  The  eggs  of  hedge-birds 
are  greenifh,  with  darkfpots;  thofe  of  crows  and  magpies, 
which  are  feen  from  beneath  through  wicker  nefts,  are  white, 
with  dark  fpots;  and  thofe  of  larks  and  partridges  are  ruffet  or 
brown,  like  their  nefts  or  fttuations. 

A thing  ftiil  more  aftonithing  is,  that  many  animals,  in  coun- 
tries covered  with  fnow,  become  white  in  winter,  and  are  faid 
to  change  their  colour  again  in  the  warmer  months,  as  bears, 
hares,  and  partiidges.  Our  domefticated  animals  loie  their  na- 
tural colours,  and  break  into  great  variety,  as  horfes,  dogs,  pi- 
geons. The  final  caufe  of  thefe  colours  is  eafily  underftood, 
as  they  ferve  fome  purpofes  of  the  animal ; but  the  efficient 
caufe  would  feem  almoft  beyond  conjecture. 

Firft,  the  choroid  coat  of  the  eye,  on  which  the  femi-tranf- 
parent  retina  is  expanded,  is  of  different  colour  in  different  ani- 
mals : in  thofe  which  feed  on  grafs  it  is  green ; from  hence  there 
would  appear  fome  ccnnecftion  between  the  colour  of  the  cho- 
roid coat  and  of  that  conftantly  painted  on  the  retina  by  the 
green  grafs.  Now,  when  the  ground  becomes  covered  with 
fnow,  it  would  feem,  that  that  action  of  the  retina  which  is 
called  whitenefs,  being  conftantly  excited  in  the  eye,  may  be 
gradually  imitated  by  me  extremities  of  the  nerves  of  touch,  or 
rete  mucofum  of  the  Ikin.  And  it  it  be  fuppofed,  that  the  ac- 
tion of  the  retina,  in  producing  the  perception  of  any  colour, 
conlifts  in  fo  diipoftng  its  own  fibres  or  iurface  as  to  reflect 
thofe  coloured  rays  only,  and  tranfmit  the  others  like  Rap-bub- 
bles, then  that  part  of  the  retina  which  gives  us  the  perception 

o£ 


Sect.  XXXIX.  5.  OF  GENERATION.  377 

of  fnow,  muff,  at  that  time,  be  white ; and  that  which  gives 
us  the  perception  of  grafs,  muft  be  green. 

Then,  if,  by  the  laws  of  imitation,  as  explained  in  Sect.  XII. 
33.  and  XXXIX.  6.  the  extremities  of  the  nerves  of  touch,  in 
the  rete  mucofum,  be  induced  into  fimilar  action,  the  fk!n,  or 
feathers,  or  hair  may,  in  like  manner,  fo  difpofe  their  extreme 
fibres,  as  to  reflect  white ; for  it  is  evident,  that  all  thefe  parts 
were  originally  obedient  to  irritative  motions  during  their 
growth,  and  probably  continue  to  be  fo ; that  thofe  irritative 
motions  are  not  liable,  in  a healthy  flate,  to  be  fucceeded  by 
fenfation ; which,  however,  is  no  uncommon  thing  in  their  dil- 
eafed  Hate,  or  in  their  infant  flate,  as  in  plica  polonica,  and  in 
very  young  pen-feathers,  which  are  flill  full  of  blood. 

It  was  fhewn  in  Seel.  XV.  on  the  Production  of  Ideas,  that 
the  moving  organ  of  fenfe,  in  fome  circumftances,  refembled 
the  object  which  produced  that  motion.  Hence  it  may  be  con- 
ceived, that  the  rete  mucofum,  which  is  the  extremity  of  the 
nerves  of  touch,  may,  by  imitating  the  motions  of  the  retina, 
become  coloured.  And  thus,  like  the  fable  of  the  cameleon,  all 
animals  may  pofTefs  a tendency  to  be  coloured  fomewhat  like 
the  colours  they  moft  frequently  infpect ; and  finally,  that  co- 
lours may  be  thus  given  to  the  egg-fliell  by  the  imagination  of 
the  female  parent ; which  fhell  is  previoufly  a mucous  mem- 
brane, endued  with  irritability,  without  which  it  could  not  cir- 
culate its  fluids,  and  increafe  in  its  bulk.  Nor  is  this  more 
wonderful  than  that  a iingle  idea  of  imagination  fliould,  in  an 
inftant,  colour  the  whole  l’urface  of  the  body  of  a bright  fcarlet, 
as  in  the  blufh  of  fhame,  though  by  a very  different  procefs. 
In  this  intricate  fubject,  nothing  but  Icofe  analogical  conjectures 
can  be  had,  which  may,  however,  lead  to  future  difeoveries ; 
but  certain  it  is,  that  both  the  change  of  the  colour  of  ani- 
mals to  white  in  the  winters  of  fnowy  countries,  and  the  fpots 
on  birds  eggs,  muft  have  fome  efficient  caufe ; lince  the  uni- 
formity of  their  production  fhews  it  cannot  arife  from  a fortui- 
tous concurrence  of  circumftances : and  how  is  this  efficient 
Caufe  to  be  detected,  or  explained,  but  from  its  analogy  to 
other  animal  facts  ? 

2.  The  nutriment  fupplied  by  the  female  parent  in  viviparous 
animals,  to  their  young  progeny,  may  be  divided  into  three  kinds, 
correfponding  with  the  age  of  the  new  creature.  1.  The  nu- 
triment contained  in  the  ovum,  as  previoufly  prepared  for  the 
embryon  in  the  ovary.  2.  The  liquor  amnii  prepared  for  the 
ficetus  in  the  uterus,  and  in  which  itfwims:  and,  lalliy,  the 
miik  prepared  in  the  pectoral  glands  of  the  new-born  child. 
There  is  reafon  to  conclude,  that  variety  of  changes  may  be 

producedj 


378  OF  GENERATION.  Sect. XXXIX. 5. 

produced,  in  the  new  animal,  from  all  thefe  fources  of  nutri- 
ment, but  particularly  from  the  firft  of  them. 

The  organs  of  digeflion  and  of  fanguification  in  adults,  and 
afterwards  thofe  of  fecretion,  prepare  or  feparate  the  particles 
proper  for  nourifhment,  from  other  combinations  of  matter,  or 
re-combine  them  into  new  kinds  of  matter,  proper  to  excite  into 
aCiion  the  filaments  which  abforb  or  attraCt  them  by  animal  ap- 
petency. In  this  proccfs  we  mud  attend  not  only  to  the  aCtion 
of  the  living  filament  which  receives  a nutritive  particle  to  its 
holom,  but  alfo  to  the  kind  of  particle,  in  refpect  to  form,  or 
free,  or  colour,  or  hardnefs,  which  is  thus  previoufly  prepared 
for  it  by  digeflion,  fanguification,  and  fecretion.  Now,  as  the 
firft  filament  of  entity  cannot  be  furnifhed  with  the  preparative 
organs  above  mentioned,  the  nutritive  particles,  which  are  at 
firft  to  be  received  by  it,  are  prepared  by  the  mother,  and  de- 
pofited  in  the  ovum  ready  for  its  reception.  Thefe  nu  ririve 
particles  muft  be  fuppofed  to  differ  in  fome  refpedts,  when  thus 
prepared  by  different  animals.  They  may  differ  in  lize,  foliditv, 
colour,  and  form  ; and  yet  may  be  iufficiently  congenial  to  the 
living  filament  to  which  they  are  applied,  as  to  excite  its  adlivitv 
by  their  ftimulus,  and  its  animal  appetency  to  receive  them,  and 
to  com, bine  them  with  itfelf  into  organization. 

By  this  firft  nutriment,  thus  prepared  for  the  embryon,  is  not 
meant  the  liquor  amnii,  which  is  produced  afterwards,  nor  the 
larger  exterior  parts  of  the  white  of  the  egg;  but  the  fluid  pre- 
pared, I fuppofe,  in  the  ovary  of  viviparous  animals,  and  that 
which  immediately  furrounds  the  cicatricula  of  an  impregnated 
egg,  and  is  vifible  to  the  eye  in  a boiled  one. 

No  w,  thefe  ultimate  particles  of  animal  matter,  prepared  by 
the  gb  nds  of  the  mother,  may  be  luppofed  to  refemblc  the  iimi- 
lar  ultimate  particles  which  were  prepared  for  her  own  nouri di- 
luent; that  is,  to  the  ultimate  particles  of  which  her  own  or- 
ganization confifts.  And  that  hence,  when  thel’e  become  com- 
bined with  the  new  embryon,  which,  in  its  early  ftate,  is  not 
furnifhed  with  ftomach  or  glands  to  alter  them,  that  new  em- 
bryon will  bear  fome  relemblance  to  the  mother. 

Thus  feems  to  be  the  origin  of  the  compound  forms  of  mules, 
which  evidently  partake  of  both  parents,  but  principally  of  the 
male  parent.  In  this  production  of  chimeras,  the  ancients 
feem  tc  » have  indulged  their  fancies ; whence  the  iphin-xes,  grit- 
fins.  dragons,  centaurs,  and  minotaurs,  which  are  vamfhed  irom 
moden  1 credulity. 

It  w on kl  feem,  that,  in  thefe  unnatural  conjunctions,  when 
the  nu  triment  depofited  by  the  female  was  fo  ill  adapted  to  iti- 
mulatfi'  the  living  filament,  derived  from  the  male,  into  action. 


Sect.  XXXIX.  5.  OF  GENERATION*.  379 

and  to  be  received  or  embraced  by  it,  and  combined  with  it  into 
organization,  as  not  to  produce  the  organs  neceffary  to  life,  as 
the  brain,  or  heart,  or  ftomach,  that  no  mule  was  produced. 
Where  all  the  parts  neceffary  to  life,  in  thefe  compound  ani- 
mals, were  formed  fufficiently  perfedt,  except  the  parts  of  ge- 
neration, thofe  animals  were  produced  which  are  now  called 
mules. 

The  formation  of  the  organs  of  fexual  generation,  in  contra - 
diftindtion  to  that  by  lateral  buds,  in  vegetables,  and  in  fome 
animals,  as  the  polypus,  the  taenia,  and  the  volvox,  feems  the 
chef  d’oeuvre,  the  mafter-pieee  of  nature ; as  appears  from 
many  dying  infedfs,  as  in  moths  and  butterflies,  who  feem  to 
undergo  a general  change  of  their  forms  folely  for  the  purpofe  of 
fexual  re-production  ; and  in  all  other  animals  this  organ  is  not 
complete  till  the  maturity  of  the  creature.  Whence  it  happens, 
that,  in  the  copulation  of  animals  of  different  fpecies,  the  parts  ne- 
ceffary to  life  are  frequently’coinpletelv  formed  ; but  thofe  tor  the 
purpofe  of  generation  are  defective,  as  requiring  a nicer  organi- 
zation, or  more  exadt  coincidence  of  the  particles  of  nutriment 
to  the  irritabilities  or  appetencies  of  the  original  living  filament; 
Whereas . thofe  mules  -where  all  the  parts  could  be  perfedtlv 
formed,  may  have  been  produced  in  earlier  periods  of  time,  and 
may  have  added  to  the  numbers  of  our  various  fpecies  of  ani- 
mals, as  before  obferved. 

As  this  produdtion  of  mules  is  a conftant  effecff  from  the  con- 
junction of  different  fpecies  of  animals,  thofe  between  the  horfe 
and  the  female  afs  always  refembling  the  horfe  more  than  the 
afs  ; and  thole,  on  the  contrary,  between  the  male  afs  and  the 
mare  always  refembling  the  afs  more  than  the  mare ; it  cannot 
be  afcribed  to  the  imagination  of  the  male  animal,  which  can- 
not be  fuppofed  to  operate  fo  uniformly ; but  to  the  form  of  the 
firft  nutritive  particles,  and  to  their  peculiar  ftimulus  exciting 
the  living  filament  to  feledt  and  combine  them  with  it lelf. 
There  is  a fifnilar  uniformity  of  e fie 61  in  refpedt  to  the  colour 
bf  the  progeny  produced  between  a white  man  and  a black 
woman,  which,  if  1 am  well  informed,  is  always  of  the  mulatto 
kind,  or  a mixture  ot  the  two  ; which  may  perhaps  be  imputed 
to  the  peculiar  form  of  the  particles  of  nutriment  fupplied  to- 
the  embryon  by  the  mother  at  the  early  period  of  its  exifience, 
and  their  peculiar  ftimulus  ; as  this  effedt,  like  that  of  the  mule 
progeny  above  treated  of,  is  uniform  and  confiftent,  and  cannot 
therefore  be  afcribed  to  the  imagination  of  either  of  the  parents. 

Dr.  Thunberg  obferves,  in  his  Journey  to  the  Cape  of 
Good  Hope,  that  there  are  fome  families,  which  have  defcended 
from  blacks  in  the  female  line  for  three  generations.  The  firft 

Ddd  generation 


3 OF  GENERATION.  Sect.  XXXIX.  3. 

generation  proceeding  from  an  European,  who  married  a tawny 
Have,  remains  tawny,  hut  approaches  to  a white  complexion  ; 
but  the  children  of  the  third  generation,  mixed  with  Europeans, 
become  quite  white,  and  are  often  remarkably  beautiful,  v.  i.p. 

1 12. 

When  the  embryon  has  produced  a placenta,  and  furnifhed 
itfelf  with  veffels  for  feledlion  of  nutritious  particles,  and  for 
oxygenation  of  them,  no  great  change  in  its  form  or  colour 
is  likely  to  be  produced  by  the  particles  of  fuftenance  it  now 
takes  from  the  fluid,  in  which  it  is  imrnerfed ; becaufe  it  has 
now  acquired  organs  to  alter  or  new  combine  them.  Hence 
it  continues  to  grow,  whether  this  fluid,  in  which  it  fwims, 
be  formed  by  the  uterus,  or  by  any  other  cavity  of  the  body, 
as  in  extra-uterine  sjeftation  ; and  which  would  feem  to  be 
produced  by  the  ftimulus  of  the  foetus  on  the  fides  of  the  cavity, 
where  it  is  found,  as  mentioned  before.  And  thirdly,  there  is 
iliil  lefs  reaion  to  expedf  any  unnatural  change  to  happen  to 
the  child,  after  its  birth,  from  the  difference  of  the  milk  it  now 
takes ; becaufe  it  has  acquired  a ftomach,  and  lungs,  and 
glands,  of  fufficient  power  to  decompofe  and  re-combine  the 
milk  ; and  thus  to  prepare  from  it  the  various  kinds  of  nutritious 
particles,  which  the  appetencies  of  the  various  fibrils  or  nerves 
may  require. 

From  all  this  reafoning  I would  conclude,  that  though  die 
imagination  of  the  female  may  be  fuppofed  to  affedt  the  em- 
bryon, by  producing  a difference  in  its  early  nutriment;  yet 
that  no  fuch  power  can  affedf  it  after  it  has  obtained  a placenta 
and  other  organs,  which  may  feledf  or  change  the  food  which 
is  prefented  to  it  either  in  the  liquor  amnii  or  in  the  milk.  Now, 
as  the  eggs  in  pullets,  like  the  feeds  in  vegetables,  are  produc- 
ed gradually,  long  before  they  are  impregnated,  it  does  not  ap- 
pear how  any  fudden  effect  of  imagination  of  the  mother,  at  the 
time  of  impregnation,  can  produce  any  confiderable  change  in 
the  nutriment  already  thus  laid  up  for  the  expected  or  defired 
embryon.  And  that  hence  any  changes  of  the  embryon,  ex- 
cept thofe  uniform  ones  in  the  production  of  mules  and  mu- 
lattoes,  more  probably  depend  on  the  imagination  of  the  male 
parent.  At  the  lame  time  it  feems  manifeft,  that  thofe  mon- 
ftrous  births,  which  confift  in  feme  deficiencies  only,  or  fome 
redundancies  of  parts,  originate  from  the  deficiency  or  redun- 
dance of  the  firft  nutriment  prepaied  in  the  ovary,  oj  in  the  part 
of  the  egg  immediately  furrounding  the  cicatricuia,  as  delcrib- 
ed  above ; and  which  continues  fome  time  to  excite  the  firft 
living  filament  into  adfion,  after  the  limple  animal  is  complet- 
ed; or  ceafca  to  excite  it.  before  the  complete  form  is  accorn- 

» plifhed. 


'Sect.  XXXIX.  6.  OF  GENERATION.  381 

plifhed.  The  former  of  thefe  circumftances  is  evinced  by  the 
.eggs  with  doable  yolks,  which  frequently  happen  to  our  do- 
mefticated  poultry,  and  which,  I believe,  are  fo  formed  before 
impregnation,  but  which  would  be  well  worth  attending  to 
both  before  and  after  impregnation,  as  it  is  probable  fomething 
valuable  on  this  fubjerit  might  be  learnt  from  them.  The  latter 
circumftance,  or  that  of  deficiency  of  original  nutriment,  may 
be  deduced  from  reverfe  analogy. 

There  are,  however,  other  kinds  of  monflrrous  births,  which 
neither  depend  on  deficiency  of  parts,  nor  fupernumerary  ones; 
nor  are  owing  to  the  conjunrition  of  animals  of  different  fpe- 
cies;  but  which  appear  to  be  new  conformations,  or  new  dif- 
pofitions  of  parts  in  refperit  to  each  other,  and  which,  like  the 
variation  of  colours  and  forms  of  our  domefticated  animals, 
and  probably  the  fexual  parts  of  all  animals,  may  depend  on  the 
imagination  of  the  male  parent,  which  we  now  come  to  con- 
sider. 

VI.  1.  The  nice  arilions  of  the  extremities  of  our  various 
glands  are  exhibited  in  their  various  productions,  which  are  be- 
lieved to  be  made  by  the  gland,  and  not  previoufiy  to  exift  as 
fuch  in  the  blood.  Thus  the  glands,  which  conftitute  the  liver, 
make  bile;  thofe  of  the  ftomach  make  gaffric  acid;  thofe  be- 
neath the  jaw,  faliva;  thofe  of  the  ears,  ear-wax,  and  the  like. 
Every  kind  of  gland  mud  poffefs  a peculiar  irritability,  and  pro- 
bably a fenfibility,  at  the  early  ftate  of  its  exiftence ; and  muff 
."be  furnifhed  with  a nerve  of  l'enfe,  or  of  motion,  to  perceive, 
and  to  felecd,  and  to  combine  the  particles,  which  compofe  the 
fluid  it  fecretes.  And  this  ne'rve  of  fenfe,  which  perceives  the 
different  articles  which  compofe  the  blood,  muff  atleaft  be  con- 
ceived to  be  as  fine  and  fubtile  an  organ  as  the  optic  or  audi- 
tory nerve,  which  perceives  light  or  found.  See  Serif.  XIV.  9. 

But  in  nothing  is  this  nice  action  of  the  extremities  of  the 
blood-veffels  fo  wonderful  as  in  the  production  of  -contagious- 
matter.  A fmall  drop  of  variolous  contagion,  diffufed  in  the 
blood,,  or  perhaps  only  by  being  inferted  beneath  the  cuticle, 
after  a time,  (as  about  a quarter  of  a lunation)  excites  the  ex- 
treme veffels  of  the  Ikin  into  certain  motions,  which  produce  a 
fimilar  contagious  material,  filling  it  with  a thoufand  puftules. 
So  that  by  irritation,  or  by  fenfation  in  confluence  ot  irritatiou, 
or  bv  affociation  of  motions,  a material  is  formed  by  the  extre- 
mities of  certain  cutaneous  veffels,  exactly  fimilar  to  the  ftimu- 
lating  material,  which  caufed  the  irritation,  or  coniequent  fen- 
fation, or  affociation. 

Many  glands  of  the  body  have  their  motions,  and  in  confe- 
quence  their  fecreted  fluid,  affected  by  pleafureable  or  painful 

ideas. 


OF  GENERATION.  Sect.  XXXIX.  6. 


jdeas,  fince  thev  are,  in  many  infiances,  influenced  by  fenfltive  af- 
fociations,  as  well  as  by  the  irritations  of  the  particles  of  the  pall- 
ing blood.  Thus  the  idea  of  meat,  excited  in  the  minds  of  hun- 
gry dogs,  by  their  fenfe  of  vifion,  or  of  fmell,  increafes  thedif- 
charge  of  faliva,  both  in  quantity  and  vilcidity  ; as  is  feen  in  its 
hanging  down  in  tl treads  from  their  mouths,  as  they  Hand  round 
a dinner-table.  The  fenfations  ot  pleafure,  or  of  pain,  of  pe- 
culiar kinds,  excite,  in  the  fame  manner,  a great  uifcharge  of  - 
fears;  which  appear  alfo  to  be  more  faline  at  the  time  of  their 
fecretion,  from  their  inflaming  the  eyes  and  eye-lids.  The 
palenefs  from  fear,  and  the  blufh  of  fhame,  and  of  joy,  are 
other  in  fiances  of  the  efFe£ls  of  painful,  or  pleafureable  fenfa- 
tions, on  the  extremities  of  the  arterial  fyftem. 

It  is  probable,  that  the  pleafureable  lenfation  excited  in  the 
ftomach  by  food,  as  well  as  its  irritation,  contributes  to  excite  • 
into  adtion  the  gaflric  glands,  and  to  produce  a greater  fecre- 
tion of  their  fluids.  The  fame  probably  occurs  in  the  fecretion 
of  bile;  that  is,  that  the  pleafureable  fenfation  excited  in  the 
ftomach,  affects  this  fecretion  by  fenfltive  affociation,  as  well 
as  by  irritative  affociation. 

And,  laflly,  it  would  feern  that  all  the  glands  in  the  body 
have  their  fecreted  fluids  affedted,  in  quantity  and  quality,  by 
the  pleafureable  or  painful  fenfations  which  produce  or  accom- 
pany thofe  fecretions.  And  that  the  pleaiureable  lenlations 
ariflng  from  thefe  fecretions  may  conff  itute  the  unnamed  plea- 
fure of  exiftence,  which  is  contrary  to  what  is  meant  by  tasdium 
vitae,  or  ennui,  and  by  which  we  fometimes  feel  ourfelves  happy, 
without  being  able  to  afcribe  it  to  any  mental  caufe,  as  after  an 
agreeable  meal,  or  in  the  beginning  of  intoxication. 

Now,  it  would  appear,  that  no  fecretion  or  excretion  of 
fluid  is  attended  with  fo  much  agreeable  fenfation  as  that  of, 
the  femen;  and  it  would  thence  follow,  that  the  glands,  which 
perform  this  fecretion,  are  more  likely  to  be  much  affedted  by 
their  catenations  with  pleaiureable  lenlations.  This  circum- 
ftance  is  certain,  that  much  more  of  this  fluid  is  produced  in  a 
given  time,  when  the  objedt  of  its  excluflon  is  agreeable  to 
the  mind. 

2.  A forcible  argument,  which  fhews  the  neceffity  of 
pleafureable  fenfation  to  copulation,  is,  that  the  act  cannot  be 
performed  without  it ; it  is  eaflly  interrupted  by  the  pain  of 
fear  or  bafhfulnefs  ; and  no  efforts  of  volition  or  of  irritation  t 
c.aneffedt  this  procefs,  except  fuch  as  induce  pleaiureable  ideas 
or  fenfations.  See  Sect.  XXX11T.  i.  i. 

' A curious  analogical  circumftunce  attending  hermaphrodite  1 
infects,  as  fnails  and  worms,  it  ill  further  ill  nitrates  this  theory ; ! 
t hp  1 


§ect.XXXIX.6.  OF  GENERATION.  383 

if  the  fnail  or  worm  could  have  impregnated  itfelf,  there  might 
have  been  a laving  or  a large  male  apparatus ; but  as  this  is 
not  fo  ordered  by  nature,  but  each  fnail  and  worm  reciprocally 
receives  and  gives  impregnation,  it  appears,  that  a pleafureable 
excitation  feems  alfo  to  have  been  required. 

This  wonderful  circumftance  of  many  infebfs  being  her- 
maphrodites, and  at  the  fame  time  not  having  power  to  im- 
pregnate themfelves,  is  attended  to  by  Dr.  Lifter,  in  his  Ex- 
ercitationes  Anatom,  de  Limacibus,  p.  145:  who,  amongft 
many  other  final  caufes,  which  he  adduces  to  account  for  it, 
adds,  ut  tarn  triftibus  et  frigidis  animalibus  majori  cum  voluptate 
perficiatur  venus. 

• There  is,  however,  another  final  caufe,  to  which  this  cir- 
cumftance may  be  imputed  : it  was  obferved  above,  that  vege- 
table buds  and  bulbs,  which  are  produced  without  a mother, 
are  always  exabt  refemblances  of  their  parent;  as  appears  in 
grafting  fruit-trees,  and  in  the  flower-buds  of  the  dioceous 
plants,  which  are  always  of  the  fame  fex,  on  the  fame  tree; 
hence  thofe  hermaphrodite  infebts,  if  they  could  have  produced 
young  without  a mother,  would  not  have  been  capable  of  that 
change  or  improvement,  which  is  feen  in  all  other  animals, 
and  in  thofe  vegetables  which  are  procreated  by  the  male 
embryon  received  and  nourifhed  by  the  female.  And  it  is  hence 
probable,  that  if  vegetables  could  only  have  been  produced  by 
buds  and  bulbs,  and  not  by  fexual  generation,  that  there  would 
not,  at  this  time,  have  exifted  one  thoufandth  part  of  their 
preferit  number  of  fpecies,  which  have  probably  been  original- 
ly mule  productions ; nor  could  any  kind  ot  improvement  or 
change  have  happened  to  them,  except  by  the  difference  of  foil 
br  climate. 

3.  I conclude,  that  the  imagination  of  the  male,  at  the  time 
of  copulation,  or  at  the  time  of  the  fecretion  of  the  femen,  may 
fo  affebt  this  fecretion  by  irritative  or  fenfitive  aflociation, 
as  defcribed  in  No.  5.  1.  of  this  feblion,  as  to  caufe  the  pro- 
duction of  fimilarity  of  form  and  of  features,  with  the  diflinc- 
tion  of  fex ; as  the  motions  of  the  chiffel  of  the  turner  imitate 
or  correfpond  with  thofe  of  the  ideas  of  the  artift.  It  is  not 
here  to  be  underftood,  that  the  firft  living  fibre,  which  is  to 
form  an  animal,  is  produced  with  any  fimilarity  of  form  to  the 
future  animal ; but  with  propenfities,  or  appetencies,  which 
fhall  produce,  by  accretion  of  parts,  the  fimilarity  of  form,  fea- 
ture, or  fex,  correfponding  to  the  imagination  of  the  father. 

Our  ideas  are  movements  of  the  nerves  of  fenfe,  as  of  the 
optic  nerve  in  recollecting  vifible  ideas,  fuppofeof  a triangular 
piece  of  ivory.  The  fine  moving  fibres  of  the  retina  abt  in  a 

* manner 


OF  GENERATION.  Sect.  XXXIX.  6. 


384 

manner  to  which  I give  the  name  of  white ; and  this  adlion  is 
confined  to  a defined  part  of  it;  to  which  figure  I give  the  name 
of  triangle.  And  it  is  a preceding  pleafureable  fenfation  exifting 
in  my  mind,  which  occalions  me  to  produce  this  particular 
motion  of  the  retina,  when  no  triangle  is  prefent.  Now,  it  is 
probable,  that  the  adding  fibres  of  the  ultimate  terminations  of 
the  fecreting  apertures  of  the  veffels  of  the  tefles,  are  as  fine  as 
thofe  of  the  retina ; and  that  they  are  liable  to  be  thrown  into 
that  peculiar  adbion,  which  marks  the  fex  of  the  fecreted  em- 
bryon,  by  Sympathy  with  the  pleafureable  motions  of  the  nerves 
of  vilion,  or  of  touch;  that  is,  with  certain  ideas  of  imagina- 
tion. From  hence  it  would  appear,  that  the  world  has  long 
been  miftaken  in  al'cribing  great  power  to  the  imagination  of  the 
female;  whereas,  from  this  account  of  it,  the  real  power  of 
imagination,  in  the  add  ot  generation,  belongs  folely  to  the  male. 
See  Sed.  XII.  3.  3. 

It  may  be  objeaed  to  this  theory,  that  a man  mav  be  fup- 
pofed  to  have  in  Iris  mind  tire  idea  of  the  form  and  features  of 
the  female,  rather  than  his  own,  and  therefore  there  fhould  be 
a greater  number  of  female  births.  On  the  contrary,  the  ge- 
neral idea  of  our  own  form  occurs  to  every  one  almoft  perpe- 
tually, and  is  termed  confcioufnel's  of  our  exiftence;  and  thus 
may  effea,  that  the  number  of  males  furpafles  that  of  females. 
See  Sedd.  XV.  3.  4.  and  XVIII.  13.  And  what  further  con- 
firms this  idea  is,  that  the  male  children  mod  frequently  refem- 
ble  the  father  in  form,  or  feature,  as  well  as  in  fex;  and  the 
female  mold  frequently  referable  the  mother,  in  feature,  and 
form,  as  well  as  in  fex. 

It  may  again  be  objected,  if  a female  child  fometimes  refem- 
bles  the  failier,  and  a male  child  the  mother,  the  ideas  or  the 
father,  at  the  time  of  procreation,  muff  fuddenlv  change  from 
himfelf  to  die  mother,  at  the  very  inftant,  when  the  embryon 
is  fecreted  or  formed.  This  difficulty  ceafes  when  we  conllder, 
that  it  is  as  eafy  to  form  an  idea  of  feminine  features  with  male 
organs  of  re-production,  or  of  male  features  with  female  ones, 
as  the  contrary ; as  we  conceive  the  idea  of  a fphmx  or  mermaid, 
as  eafiiy  and  as  diftindtly  as  of  a woman.  Add  to  this,  that  at 
the  time  of  procreation,  the  ideas  of  the  male  organs,  and  of  the 
female  features,  are  often  both  excited  at  the  fame  time,  by 
contadd  cr  by  vificn. 

I afk,  in  my  turn,  is  the  fex  of  the  embryon  produced  bv 
accident?  Certainly,  whatever  is  produced  has  a caufe;  but 
when  this  caufe  is  too  minute  for  our  comprehcnfion,  the  effect 
is  laid,  in  common  language,  to  happen  by  chance,  as  in  throw- 
ing a certain  number  on  dice.  Now,  what  caufe  can  occa- 

fionally 


Sect.  XXXIX.  6.  OF  GENERATION. 


385 

fionally  produce  the  male  or  female  character  of  the  embryon, 
but  the  peculiar  adtions  of  thofe  glands  which  form  the  em- 
bryon  ? And  what  can  influence  or  govern  thefe  adtions  of  the 
gland,  but  its  affbciations  or  catenations  with  other  fenfitive 
motions  ? Nor  is  this  more  extraordinary  than  that  the  catena- 
tions of  irritative  motions,  with  the  apparent  vibrations  of  ob- 
jects at  fea,  fhould  produce  ficknefs  ot  the  ftomacb ; or  that  a 
iraufeous  ftory  fhould  occafion  vomiting. 

4.  An  argument,  which  evinces  the  effect  of  imagination 
on  the  firft  rudiment  of  the  embryon,  may  be  deduced  from 
the  production  of  feme  peculiar  monflers:  fuch,  for  inftance, 
as  thofe  which  have  two  heads  joined  to  one  body,  and  thofe' 
which  have  two  bodies  joined  to  one  head ; of  which  frequent 
examples  occur  amongft  our  domefticated  quadrupeds  and 
poultry.  It  is  abfurd  to  fuppofe,  that  fuch  forms  could  exiflr 
in  primordeal  germs,  as  explained  in  No.  IV.  4.  of  this  fedtion. 
Nor  rs  it  poiTible  that  fuch  deformities  could  be  produced  by 
the  growth  of  two  embryons,  or  living  filaments,  which  fhould 
afterwards  adhere  together ; as  the  head  and  tail  part  of  differ- 
ent polypi  are  fa  id  to  do  (Blumenbach  on  Generation,  Cadel, 
London) ; fince,  in  that  cafe,  one  embryon,  or  living  filament, 
muff  have  begun  to  form  one  part  firft,  and  the  other  another 
part  firft.  But  ftrch  monftrous  conformations  become  lefs 
difficult  to  comprehend,  when  they  are  confidered  as  an  effedt 
of  the  imagination,  as  before  explained,  on  the  living  filament 
at  the  time  of  its  fecretion;  and  that  fuch  duplicature  of  limbs 
were  produced  by  accretion  of  new  parts,  in  confequence  of 
propenfities,  or  animal  appetencies,  thus  acquired  from  the 
male  parent. 

For  inftance;  I can  conceive,  if  a turkey-cock  fhould  be- 
hold a rabbit,  or  a frog,  at  the  time  of  procreation,  that  it 
might  happen,  that  a forcible  or  even  a pleafureable  idea  of  the 
form  of  a quadruped  might  fo  occupy  his  imagination,  as  to 
eaufe  a tendency  in  tbenafcent  filament  to  refemble  fuch  a form 
by  the  appofition  of  a duplicature  of  limbs.  Experiments  on 
tire  production  of  mules  and  monfters  would  be  worthy  the 
attention  of  a Spallanzani,  and  might  throw  much  light  upon 
this  fubjedt,  which  at  prefent  muft  be  explained  by  conjectural- 
analogies. 

The  wonderful  effedt  of  imagination,  both  in  tire  male  and 
female  parent,  is  fhewnin  the  produdtion  of  a kind  of  milk  in 
the  crops  both  of  the  male  and  female  pigeons,  after  the  birth  of 
their  young,  as  obferved  by  Mr.  Hunter,  and  mentioned  be- 
fore. 1 o this  fhould  be  added,  that  there  are  fome  inftances 
of  men  having  had  milk  fecreted  in  their  breads,  and  who  have 


OF  GENERATION.  Fect.  XXXIX.  6: 


3S6 

given  fuck  to  children,  as  recorded  by  Mr.  Buffon.  This 
effedt  of  imagination,  of  both  the  male  and  female  parent, 
feems  to  have  been  attended  to  in  very  early  times;  Jacob  is 
faid  not  only  to  have  placed  rods  of  trees,  in  part  ftripped  of 
their  bark,  fo  as  to  appear  fpotted,  but  alfo  to  have  placed  fpot- 
ted  lambs  before  the  flocks,  at  the  time  of  their  copulation. 
Genefls,  chap,  xxx.  verfe  40. 

5.  In  refpeil  to  the  imagination  of  the  mother,  it  is  difficult 
to  comprehend,  how  this  can  produce  any  alteration  in  the 
foetus,  except  by  affedling  the  nutriment  laid  up  for  its  firfl  re- 
ception, as  defcribed  in  No.  V.  2.  of  this  fedfion,  or  by  affect- 
ing the  nourifhment  or  oxygenation  with  which  (he  fupplies 
it  afterwards.  Perpetual  anxiety  may  probably  affedt  the 
fecretion  of  the  liquor  amnii  into  the  uterus,  as  it  enfeebles 
the  whole  fyflem;  and  fudden  fear  is  a frequent  caufe  of  mif- 
carriage;  for  fear,  contrary  to  joy,  decreafes  for  a time  the 
adtion  of  the  extremities  of  the  arterial  fyflem ; hence  hidden 
palenefs  l'ucceeds,  and  a fhrinking  or  contraction  of  the  veflels 
of  the  fkin,  and  other  membranes.  By  this  circumftance,  I 
imagine,  the  terminations  of  the  placental  veflels  are  detached 
from  their  adhehons,  or  infertions,  into  the  membrane  of  the 
uterus  ; and  the  death  of  the  child  fucceeds,  and  confequent 
mifcarriage. 

Of  this  I recoiled!;  a remarkable  inftance,  which  could  be 
afcribed  to  no  other  caufe,  and  which  I fliall  therefore  relate 
in  few  words.  A healthy  young  woman,  about  twenty  years 
of  age,  had  been  about  five  months  pregnant,  and  going  down 
into  her  cellar  to  draw  fome  beer,  was  frighted  by  a fervant- 
boy  flatting  up  from  behind  the  barrel,  where  he  had  conceal- 
ed himfelf  with  deilgn  to  alarm  the  maid-fervant,  for  whom  he 
miftook  hismiiftrefs.  She  came  with  difficulty  up  flairs,  began 
to  flood  immediately,  and  mifcarried  in  a few  hours.  She  has 
fince  borne  feveral  children,  nor  ever  had  any  tendency  to  mil- 
carry  of  any  of  them. 

In  refpedt  to  the  power  of  the  imagination  of  the  male  over 
the  form,  colour,  and  fex  of  the  progeny,  the  following  in- 
ftances  have  fallen  under  my  obfervation,  and  may  perhaps  be 
found  not  very  unfrequent,  if  they  were  more  attended  to.  I 
am  acquainted  with  a gentleman,  who  has  one  child  with  dark 
hair  and  eyes,  though  his  lady  and  himfelf  have  light  hair 
and  eyes,  and  their  other  four  children  are  like  their  parents. 
On  obfeiving  this  diflimilarity  of  one  child  to  the  others,  he 
affined  me,'  that  he  believed  it  was  his-own  imagination  that 
produced  the  difference;  and  related  to  me  the  following  (lory, 
tie  laid,  that  when  his  lady  lay  in  other  third- child,  he  became 

attached 


Sect.XXXIX.  j.  OF  GENERATION.  gSf 

attached  to  a daughter  of  one  of  his  inferior  tenants,  and  offered 
her  a bribe  for  her  favours  in  vain ; and  afterwards  a greater 
bribe,  and  was  equally  unfuccefsful ; that  the  form  of  this  girl 
dwelt  much  in  his  mind  for  fome  weeks,  and  that  the  next 
child,  which  was  the  dark-eyed  young  lady  above  mentioned, 
was  exceedingly  like,  in  both  features  and  colour,  to  the  young 
woman  who  refufed  his  addreffes. 

To  this  inftance  I mull:  add,  that  I have  known'  two  families, 
in  which,  on  account  of  an  intailed  eftate,  in  expectation* 
a male  heir  was  moll  eagerly  defired  by  the  lather ; and,  on  the 
contrary,  girls  were  produced  to  the  feventh  in  one,  and  to  the 
ninth  in  another;  and  then  they  had  each  of  them  a fon.  I 
conclude  that  the  great  defire  of  a male  heir  by  the  father  pro- 
duced rather  a difagreeable  than  an  agreeable  fenfation ; and 
that  his  ideas  dwelt  more  on  the  fear  of«generati'ng  a female, 
than  on  the  pleafureable  fenfations  or  ideas  of  his  own  male 
form  or  organs  at  the  time  of  copulation,  or  ol  the  fecretion  of 
the  femen ; and  that  hence  the  idea  of  the  female  character  was 
more  prefent  to  his  mind  than  that  of  the  male  one ; till  at  length, 
in  defpair  of  generating  a male,  thefe  ideas  ceafed,  and  thole 
of  the  male  character  prelided  at  the  genial  hour. 

7.  Hence  I conclude,  that  the  adt  of  generation  cannot 
exift  without  being  accompanied  with  ideas,  and  that  a man 
mu  If  have  at  that  time  either  a general  idea  of  his  own 
male  form,  or  of  the  form  of  his  male  organs ; or  an  idea  of 
the  female  form,  or  of  her  organs ; and  that  this  marks  the  fex, 
and  the  peculiar  refemblances  of  the  child  to  either  parent. 
From  whence  it  would  appear,  that  the  phalli,  which  were 
hung  round'the  necks  of  the  Roman  ladies,  or  worn  in  their 
hair,  might  have  effedf  in  producing  a greater  proportion  of 
male  children ; and  that  the  calipsedia,  or  art  ol  begetting  beau- 
tiful children,  and  of  procreating  either  males  or  lemales,  may 
be  taught  by  affedting  the  imagination  of  the  male-parent ; that 
is,  by  the  fine  extremities  of  the  feminal  glands  imitating  the 
addons  of  the  organs  of  fenfe,  either  of  fight  or  touch.  But 
the  manner  of  accomplifhing  this  cannot  be  unfolded  with 
fufficient  delicacy  for  the  public  eye,  but  may  be  worth  the  at- 
tention of  thofe  who  are  ferioufly  interefted  in  the  procrea- 
tion of  a male  or  female  child. 

Recapitulation. 

VII.  1.  A certain  quantity  of  nutritive  particles  are  produced 
by  the  female  parent  before  impregnation,  which  require  no 
further  digeftion,  Secretion  or  oxygenation.  Such  are  feen  in 
the  unimpregnated  eggs  of  birds,  and  in  the  unimpregnated 
feed-vcffels  of  vegetables.  , 


3#S  .OF  GENERATION.  Sect.  XXXIX.  7. 

2.  A living  filament  is  produced  by  the  male,  which  being 
inferted  amidft  thefe  firft  nutritive  particles,  is  ftimulatcd  into 
adiion  by  them;  and,  in  confequence  of  this  adlion,  fome  of 
the  nutritive  particles  are  embraced,  and  added  to  the  original 
living  filament;  in  the  fame  manner  as  common  nutrition  is 
performed  in  the  adult  animal. 

3.  Then  this  new  organization,  or  additional  part,  becomes 
ftimulated  by  the  nutritive  particles  in  its  vicinity,  and  fenfa- 
tion  is  now  fuperadded  to  irritation  ; and  other  particles  are  in 
confequence  embraced,  and  added  to  the  living  filament ; as  is 
feen  in  the  new  granulations  of  flefh  in  ulcers. 

By  the  power  of  affociation,  or  by  irritation,  the  parts  al- 
ready produced  continue  their  motions,  and  new  ones  are  ad- 
ded by  ienfation,  as  above  mentioned;  and  laftly,  bv  volition; 
which  la  ft  fenforial  power  is  proved  to  exift  in  the  foetus  in  its 
maturer  age,  becaufe  it  has  evidently  periods  of  activity  and  of 
Seeping ; which  la  ft  is  another  word  for  a temporary  fufpen- 
fton  of  volition. 

The  original  living  filament  may  be  conceived  to  poffefs  a 
power  of  repulfing  the  particles  applied  to  certain  parts  of  it, 
as  well  as  of  embracing  others,  which  ftimulate  other  parts  of 
it;  as  thefe  powers  exift  in  different  parts  of  the  mature  ani- 
mal ; thus  the  mouth  of  every  gland  embraces  the  particles  of 
fluid  which  fuits  its  appetency,  and  its  excretory  duel  repul- 
fes  thole  particles  which  aFe  difagreeable  to  it. 

4.  Thus  the  outline,  or  miniature  of  the  new  animal,  is 
produced  gradually,  but  in  no  great  length  of  time;  becaufe  the 
original  nutritive  particles  require  no  previous  preparation  by 
digeftion,  fecretion,  and  oxygenation  ; but  require  limply  the 
feledlion  and  appofition,  which  is  performed  by  the  living  fila- 
ment. Mr.  Biumenbach  fays,  that  he  poffcffes  a human  foe- 
tus of  only  five  weeks  old,  which  is  the  fize  or  a common  bee, 
and  has  all  the  features  of  the  face,  every  huger,  and  every 
toe,  complete  ; and  in  which  the  organs  of  generation  are  dif- 
tindfly  feen.  P.  76.  In  another  foetus,  whole  head  was  not 
larger  than  a pea,  the  whole  of  the  balls  of  the  fkull,  with  all 
ks  depreffions,  apertures,  and  proceffes,  were  marked  in  the 
moft  fharp  and  diftindl  manner,  though  without  any  offifica- 
tion.  Ibid. 

5.  In  fome  cafes,  by  the  nutriment  originally  depofited  by 
the  mother,  the  filament  acquires  parts  not  exactly  limilar  to 
thofe  of  tire  father,  as  in  the  produdlion  of  mules  and  nvulat- 
toes.  In  other  cafes  the  deficiency  of  this  original  nutriment, 
caufes  deficiencies  of  the  extreme  parts  of  tht  feetus,  which  arc 
laft  formed,  as  the  lingers,  toes,  lips.  In  other  cales,  a dupli- 

cature 


Sect.  XXXIX.  7.  OF  GENERATION.  3S9 

cature  of  limbs  are  caufed  by  the  fuperabundance  of  this  origi- 
nal nutritive  fluid,  as  in  the  double  yolks  of  eggs,  and  th; 
chickens  from  them  with  four  legs  and  four  wings.  But  the 
. production  of  other  monilers,  as  thofe  with  two  heads,  or  with 
parts  placed  in  wrong  fituations,  feems  to  arife  from  the  ima- 
gination of  the  father  being,  in  forne  manner,  imitated  by  the 
extreme  veffels  of  the  feminal  glands ; as  the  colours  of  the 
fpots  on  eggs,  and  the  change  of  the  colour  of  the  hair  and 
feathers  of  -animals  by  domeftication,  may  be  caufed,  in  the 
fame  manner,  by  the  imagination  of  the  mother. 

6.  The  living  filament  is  a part  of  the  father,  and  has  there- 
fore certain  propenfities,  or  appetencies,  which  belong  to  him  ; 
which  may  have  been  gradually  acquired  during  a million  of 
generations,  even  from  the  infancy  of  the  habitable. earth  ; and 
which  now  poffefles  fuch  properties,  as  would  render,  by  the 
appofition  of  nutritious-particles,  the  new  foetus  exactly  fimilar 
to  the  father ; as  occurs  in  the  buds  and  bulbs  of  vegetables,  and  in 
the  polypus,  and  taenia  or  tape-worm.  But  as  the  firft  nutri- 
ment is  fupplied  by  the  mother,  and  therefore  refembles  fuch 
.nutritive  particles  as  have  been  ufed  for  her  own  nutriment. or 
growth,  the  progeny  takes,  in  part,  the  likenefs  of. the  mother. 

Other  fimilarity  of  the  excitability,  or  of  the  form  of  the 
male  parent,  fuch  as  the  broad  or  narrow  fhoulders,  or  fuch 
as  conftitute  certain  hereditary  difeafes,  as  icrophula,  epilepfy, 
infanity,  have  their  origin  produced  in  one,  or  perhaps  two  ge- 
nerations; as  in  the  progeny  of  thofe  who  drink  much  vinous 
fpirits;  and  thofe  hereditary  propenfities  ceafe  again,  as  I have' 
obferved,  if  one  or  two  fober  generations  fucceed ; otherwise 
.the:  family  becomes  extinct. 

This  living  filament  from  the  father,  is  alfo  liable  to  have  its 
propenfities,  or  appetencies,  altered,  at  the  time  of  its  produc- 
tion, by  the  imagination  of  the  male  parent;  the  extremities  of 
the  feminal  glands,  imitating  the  motions  of  the  organs  of  fenfe, 
and  thus  the  fex  of  the  embiyon  is  produced  ; which  may  be 
.thus  made  a male  or  a female,  by  affecting  the  imagination  of 
the  father  at  the  time  of  impregnation.  See  Se6t.  XXXIX.  6. 
3.  and  7. 

7.  After  the  feetus  is  thus  completely  formed,  together  with 
its  umbilical  veffels  and  placenta,  it  is  now  fupplied  with  a dif- 
ferent kind  of  food,  as  appears  by  the  difference  of  confiflency 
of  the  different  parts  of  the  white  of  the  egg,  and  of  the  liquor 
amnii ; for  it  has  now  acquired  organs  for  digeftion  or  fecre- 
tion,  and  for  oxygenation,  though  thev  are  as  yet  feeble ; which 
can,  in  fome  degree,  change,  as  well  as  fele£t,  the  nutritive  par- 
ticles which  are  now  prefented  to  it;  but  may  yet  be  affected 

by 


39o  OF  GENERATION.  Sect.  XXXIX.  7. 

by  the  deficiency  of  the  quantity  of  nutrition  fup plied  by  the 
mother,  or  by  the  degree  ot  oxygenation  fupplied  to  its  placenta 
by  the  maternal  blood. 

The  augmentation  of  the  complete  foetus,  bv  additional  par- 
ticles of  nutriment,  is  not  accompliftied  by  diftention  only,  bur 
by  apportion  to  every  part,  both  external  and  internal;  each 
of  which  acquires,  by  animal  appetencies,  the  new  addition  of 
the  particles  which  it  wants.  And  hence,  the  enlarged  parts 
are  kept  iimilar  to  their  prototypes,  and  may  be  faid  to  be  ex- 
tended ; but  their  extenfion  muft  be  conceived  only  as  a necef- 
fary  confequence  of  the  enlargement  of  all  their  parts  by  appo- 
rtion of  new  particles. 

Hence  the  new  appofition  of  parts  is  not  produced  bv  capil- 
lary attradli  on,  becaufe  the  whole  is  extended;  whereas  ca- 
pillary attraction  would  rather  tend  to  bring  the  Tides  of  flexible 
tubes  together,  and  not  to  diftend  them.  Nor  is  it  produced 
by  chemical  affinities  ; for  then  a folution  of  continuity  would 
fucceed,  as  when  fugar  is  diffolved  in  water:  but  it  is  produced 
by  an  animal  procefs,  which  is  the  confequence  of  irritation  or 
fenfation,  and  which  may  be  termed  animal  appetency. 

This  is  further  evinced  from  experiments,  which  have  been 
inftituted  to  flhew,  that  a living  mufcle  of  an  animal  bodv  re- 
quires greater  force  to  break  it,  than  a fimilar  mufcle  of  a dead 
body.  Which  evinces,  that  befides  the  attraction  of  cohdlon, 
which  all  matter  poffeflfes,  and  befides  the  chemical  attractions 
of  affinities,  which  hold  many  bodies  together,  there  is  an  ani- 
mal adhefion,  which  adds  vigour  to  thefe  common  laws  of  the 
inanimate  world. 

8.  At  the  nativity  of  a child,  it  depofits  the  placenta  or  gills, 
and,  by  expanding  its  lungs,  acquires  more  plentiful  oxygenation 
from  the  currents  of  air,  which  it  muft  now  continue  perpe- 
tually to  refpire  to  the  end  of  its  life;  as  it  now  quits  the  liquid 
Hement,  in  which  it  was  produced,  and,  like  the  tadpole  when 
it  changes  into  a frog,  becomes  an  aerial  animal. 

9.  As  the  habitable  parts  of  the  earth  have  been,  and  conti- 
nue to  be,  perpetually  increalingbv  the  production  of  fea-lhells 
and  corallines,  and  bv  the  recrements  of  other  animals  and 
vegetables ; fo,  from  the  beginning  ot  the  exiftence  ot  this  terra- 
queous globe,  the  animals  which  inhabit  it  have  conftantly 
improved,  and  are  ftill  in  a ftate  ot  progrelfive  improvement. 

This  idea  of  the  gradual  generation  of  all  things  lcerns  to 
have  been  as  familiar  to  the  ancient  philofophers  as  to  the 
modern  ones ; and  to  have  given  rife  to  the  beautiful  hierogly- 
' phie  figure  of  the  ^0 to?  uov,  or  firft  great  egg,  produced  bv 
WIGHT;  that  is,  whofe  origin  is  involved  in  obfeuritv,  and 

animated 


Sect.  XXXIX.  8.  OF  GENERATION.  391 

animated  by  £§o;;  that  is,  by  Divine  Love;  from  whence 
proceeded  all  things  which  exid. 

Conclujion. 

VIII.  1.  Cause  and  effect  may  be  confidered  as  the 
progreffion,  or  fucceffive  motions,  of  the  parts  of  the  great 
iydem  of  Nature.  The  date  of  things,  at  this  moment,  is  the 
effedt  of  the  date  of  things  which  exifted  in  the  preceding 
moment,  and  the  caufe  of  the  date  of  things  which  fhall  exid 
in  the  next  moment. 

Thel'e  caufes  and  effedbs  may  be  more  eafily  comprehended, 
if  motion  be  confidered  as  a change  of  the  figure  of  a group  of 
bodies,  as  propofed  in  Seed.  XIV.  2.  2.  inafmuch  as  our  ideas 
of  vidble  or  tangible  objects  are  more  didindt  than  our  ab- 
dracbed  ideas  of  their  motions.  Now,  the  change  of  the  confi- 
guration of  the  fydem  of  nature,  at  this  moment,  mud  be  an 
effedt  of  the  preceding  configuration,  for  a change  of  configura- 
tion cannot  exid  without  a previous  condguration ; and  the 
proximate  caufe  of  every  effedt  mud  immediately  precede  that 
effedb.  For  example;  a moving  ivory  ball  could  not  proceed 
onwards,  unlefs  it  had  previoudy  began  to  proceed,  or  unlefs 
an  impulfe  had  been  previoudy  given  it;  which  previous  mo- 
tion or  impulfe  conditutes  a part  of  the  lad  fituation  of  things. 

As  the  effects  produced  in  this  moment  of  time  become  caufes 
in  the  next,  we  may  condder  the  progredive  motions  of  objects 
as  a chain  of  caufes  only ; w'nofe  drib  link  proceeded  from  the 
great  Creator,  and  which  have  exided  from  the  beginning  of 
the  created  univerfe,  and  are  perpetually  proceeding. 

2.  Thefe  caufes  may  be  conveniently  divided  into  two  kinds, 
efficient  and  inert  caufes  ; according  with  the  two  kinds  of  en- 
tity fuppofed  to  exid  in  the  natural  world,  which  may  be  term- 
ed matter  andfpirit,  as  propofed  in  Seel.  I.  and  further  treated 
of  in  Sedb.  XIV.  The  efficient  caufes  of  motion,  or  new 
condguration,  conuft  either  of  the  principle  of  general  gravita- 
tion, which  adluates  the  fun  and  planets ; or  of  the  principle 
of  particular  gravitation,  as  in  eledbricitv,  magnetifm,  heat ; 
or  of  the  principle  of  chemical  affinity,  as  in  combudion,  fer- 
mentation, combination  ; or  of  the  principle  of  organic  life,  as 
in  the  contra 6lion  of  vegetable  and  animal  dbres.  The  inert 
caufes  of  motion,  or  new  condguration,  condd  of  the  parts 
of  matter  which  are  introduced  within  the  fpheres  of  activity 
of  the  principles  above  deferibed.  Thus,  when  an  apple  falls 
on  the  ground,  the  principle  of  gravitation  is  the  efficient  caufe, 
and  the  matter  of  the  apple  the  inert  caufe.  If  a bar  of  iron  be 
approximated  to  a magnet,  it  may  be  termed  the  inert  caufe  of 
* * . the 


OF  GENERATION.  Sect.XXXIX.-8. 


392 

the  motion,  which  brings  thefe  two  bodies  into  contact ; while 
the  magnetic  principle  may  be  termed  the  efficient  caufe.  In 
the  lame  manner,  the  fibres  which  conftirute  the  retina  may 
be  called  the  inert  caul'e  of  the  motions  of  that  orjan  in  vifion, 
while  the  fenforial  power  may  be  termed  the  efficient  caufe. 

3.  Another  more  common  diftribution  of  the  perpetual  chain 

of  caufes  and  effects,  which  conftitute  the  motions,  or  changing 
configurations,  of  the  natural  world,  is  into  active  and  paffive. 
Thus,  if  a ball  in  motion  impinges  againft  another  ball  at  reft, 
and  communicates  its  motion  to  it,  the  former  ball  is  fa  id  to 
a dt,  and  the  latter  to  be  adted  upon  In  this  fenfe  of  the  words, 

a magnet  is  faid  to  attract  iron,  and  the  prick  of  a fpur  to 
Simulate  a horie  into  exertion ; fo  that,  in  this  view  of  the  works 
of  nature,  all  things  may  be  faid  either  limply  to  exift,  cr  to  exill 
as  caufes,  or  to  exift  as  effects;  that  is,  to  exift  either  in  an 
adtive  or  paffive  ftate. 

This  diftribution  of  objedts,  and  their  motions,  or  changes  of 
pofttion,  has  been  found  l'o  convenient  for  the  purpofes  of  com- 
mon life,  that  on  this  foundation  refts  the  whole  conftrudtion 
or  theory  of  language.  The  names  of  the  things  themfelves  are 
termed,  bv  grammarians,  Nouns,  and  their  modes  of  cxiftence 
are  termed  Verbs.  The  nouns  are  divided  into  lubftantives, 
which  denote  the  principal  things  fpoken  of;  and  into  adjectives, 
which  denote  fome  circumftances,  or  lefs  kinds  of  things  be- 
longing to  the  former.  The  verbs  are  divided  into  three  kinds, 
fucli  as  denote  the  exiftence  of  things  ftmply,  as,  to  be ; or  their 
exiftence  in  an  adtive  ftate,  as,  to  eat;  or  their  exiftence  in  a 
paffive  ftate,  as,  to  be  eaten.  Whence  it  appears,  that  all  lan- 
guages conlift  only  of  nouns  and  verbs,  with  their  abbreviations, 
for  the  greater  expedition  of  communicating  our  thoughts ; as 
explained,  in  the  ingenious  work  ot  Mr.  Horne  Tooke,  who  has 
unfolded*  bv  a iingle  ftafh  of  light,  the  whole  theory  of  lan- 
guage, which  had  to  long  lain  buried  beneath  the  learned  lumber 
of  the  fchools.  Divei  lions  of  Purley.  Johnfon.  London. 

4.  A third  divifioa  of  caufes  has  been  into  proximate  and  re- 
mote : thefe  have  been  much  lpoken  ot  by  the  writers  on  medical 
fubjedts,  but  without  lufficient  precilion.  If,  to  proximate  and 
remote  caufes,  we  add  proximate  and  remote  effects,  we  ihall 
include  four  links  of  the  perpetual  chain  of  caufation  ; which 
will  be  more  convenient  for  the  dii'cuffion  o!  many  phiiofophica! 
fubjedts. 

Thus,  if  a particle  of  chvle  be  applied  to  the  mouth  of  a 
la  (Steal  veftel,  it  may  be  termed  the  remote  caule  of  the  mo- 
tions of  the  fibres,  which  compofe  the  mouth  of  that  ladteal 
veffel:  the  fenforial  power  is  the  proximate  caufe ; the  con- 

tradtion 


Sect.  XXXIX.  8.  OF  GENERATION. 


393 

tradlion  of  the  fibres  of  the  mouth  of  the  veffel  is  the  proximate 
efiFedi: ; and  their  embracing  the  particle  of  chyle  is  die  remote 
efFedi ; and  thefe  four  links  of  caufation  conftitute  abforption. 

Thus,  when  we  attend  to  the  rifing  fun,  firft  the  yellow  rays 
of  light  ftimulate  the  fenforial  power  redding  in  the  extremities 
of  the  optic  nerve — this  is  the  remote  caufe.  2.  The  fenforial 
power  is  excited  into  a IT: ate  of  activity — this  is  the  proximate 
eaufe.  3.  The  fibrous  extremities  of  the  optic  nerve  are  con- 
tradted — this  is  the  proximate  effedl.  4.  A pleafureabie  or 
painful  fenfation  is  produced  in  confequence  of  the  contradfion 
of  thefe  fibres  of  the  optic  nerve— this  is  the  remote  efFedt;  and 
thefe  four  links  of  the  chain  of  caufation  conftitute  the  fenfitive 
idea,  or  what  is  commonly  termed  the  fenfation  of  the  rifing; 
fun. 

5.  Other  caufes  have  been  announced,  by  medical  writers, 
under  the  names  of  caufa  piocatardtica,  and  caufa  proegumina, 
and  caufa  fine  qua  non.  All  which  are  links  more  or  lefs  dis- 
tant of  the  chain  of  remote  caufes. 

To  thefe  muft  be  added  the  final  caufe,  fo  called  by  many 
authors,  which  means  the  motive;  for  the  accompli  fitment  of 
which  the  preceding  chain  of  caufes  was  put  into  adtion.  The 
idea  of  a final  caufe,  therefore,  includes  that  of  a rational  mind, 
which  employs  means  to  efFedt  its  purpofes  : thus  the  defire  of 
preferving  himfelf  from  the  pain  of  cold,  which  be  has  frequent- 
ly experienced,  induces  the  favage  to  confhuct  his  hut ; the 
fixing  Hakes  into  the  ground  for  walls,  branches  of  trees  lor 
rafters,  and  turf  for  a cover,  are  a feries  of  fucceffive  voluntary 
exertions,  which  are  fo  many  means  to  produce  a certain  efi- 
fedt.  This  efFedt  of  preferving  himfelf  from  cold,  is  termed 
the  final  caufe  ; the  conftrudtion  of  the  hut  is  the  remote  efFedt ; 
the  adtion  of  the  mufcular  fibres  of  the  man,  is  the  proximate 
efFedt;  the  volition,  or  activity  of  defire  to  preferve  himfelf 
from  cold,  is  the  proximate  caufe ; and  the  pain  of  cold,  which 
excited  that  defire,  is  the  remote  caufe. 

6.  This  perpetual  chain  of  caufes  and  efFedts,  whofe  firft 
link  is  rivetted  to  the  throne  of  God,  divides  itfelf  into  innu- 
merable diverging  branches,  which,  like  the  nerves  ariling  from 
the  brain,  permeate  the  moft  minute  and  moft  remote  extremi- 
ties of  the  fyftem,  diffufing  motion  and  fenfation  to  the  whole. 
As  every  caufe  is  fuperior  in  power  to  the  efFedt  which  it  has 
produced,  fo  our  idea  of  the  power  of  the  Almighty  Creator 
becomes  more  elevated  and  fublime,  as  we  trace  the  operations 
of  nature  from  caufe  to  caufe,  climbing  up  the  links  of  thefe 
chains  of  being,  till  we  afeend  to  the  Great  Source  of  all  things. 

Hence  the  moderp  difeoveries  in  chemi fiery  and  in  geology,  by 

having 


OCULAR  SPECTRA. 


SecTt.  XL 


394 

having  traced  the  caufes  of  the  combinations  of  bodies  to  re- 
moter origins,  as  well  as  thofe  in  aftronomy,  which  dignify 
the  prefent  age,  contribute  to  enlarge  and  amplify  our  ideas  of 
the  power  of  the  Great  Firft  Caufe.  And  had  thofe  ancient 
p’nilofophers,  who  contended  that  the  world  was  formed  from 
atoms,  afcribed  their  combinations  to  certain  immutable  pro- 
perties received  from  the  hand  of  the  Creator,  fuch  as  general 
gravitation,  chemical  affinity,  or  animal  appetency,  inftead  of 
afcribing  them  to  a blind  chance,  the  doddrine  of  atoms,  as 
conftituting  or  compofing  the  material  world  by  the  variety  of 
their  combinations,  fo  far  from  leading  the  mind  to  atheifm, 
would  ftrengthen  the  demonftration  of  the  exiftence  of  a Deity, 
as  the  firft  caufe  of  all  things ; becaufe  the  analogy  refulting 
from  our  perpetual  experience  of  caufe  and  effedd  would  have 
thus  been  exemplified  through  univerfal  nature. 

The  heavens  declare  the  glory  o/God,  and  the  firmament 
Jhcweth  his  handywork  ! ■ One  day  telletk  another , and  one 
night  certifieth  another ; they  have  neither  fipecch  nor  lan- 
guage, yet  their  voice  is  gone  forth  into  all  lands , and  their 
words  into  the  ends  of  the  world.  Manifold  arc  thy  works, 
O Lord  ! in  wifdom  hafi  thou  made  them  all.  Plal.  xix. civ. 


SECT.  XL. 

On  the  Ocular  Spectra  of  Light  and  Colours,  by  Dr, 
R.  W.  Darwin,  of  Shrewfbury.  Re-printed,  by  permiffion, 
from  the  Philofophical  Tranfacdions,  vol.  Ixxvi.  p.  313. 

SpeAra  of  four  kinds.  I.  Activity  of  the  retina  in  vifion. 
2.  SpeAra  from  defeA  ef Jcnfihility.  3.  SpeAr  a from  ex- 
ec fs  of  fcnfibility.  4.  Of  direct  ocular  fpcAra.  5.  Greater 
Jlimulus  excites  the  retina  into  fpafmodic  aAion.  6.  Of 
reverfe  ocular  fpeAra.  7.  Greater  Jlimulus  excites  the 
retina  into  various  fiiccejjive  fpa)modtc  aAions.  8.  Into 
fixed  fpafmodic  aAion.  9.  Into  temporary  paralyfis.  10. 
Mifcellaneous  remarks  : 1.  Dire  A and  reverfe  fpeAra  at 
the  fame  time.  A fpeAral  halo.  Rule  to  predetermine  the 
colours  of  fpeAra.  2.  Variation  of  fpeAra  from  extra- 
neous light.  3.  Variation  of  fpeAra  in  number , figure,  and 
remiffion.  4.  Circulation  of  the  blood  in  the  eye  is  vijible. 
5.  A new  way  of  magnifying  objeAs.  Conclufion. 

WHEN  any  one  has  long  and  attentively  looked  at  a bright 
object,  as  at  die  fetting  fun,  on  ciofmg  his  eyes,  or  removing 
them,  an  image,  which  refembles  in  form  the  cbjedd  he  was 

attending 


OCULAR  SPECTRA. 


&ECT.  XL.  I. 


395 


attending  to,  continues  fome  time  to  be  vifible : this  appearance 
in  the  eye  we  thall  call  the  ocular  fpedtrum  of  that  objedt. 

Thete  ocular  fpedtra  are  of  four  kinds : ill.  Such  as  are 
owing  to  a lefs  fenfibility  of  a defined  part  of  the  retina  ; or, 
fpefira  from  defeat  of  fenfibility.  2d.  Such  as  are  owing  to 
a greater  fenfibility  or  a defined  part  of  the  retina,  or  fpedtra 
from  excefs  of  fenfbility.  3d.  Such  as  refemble  their  objedt 
in  its  colour,  as  well  as  form,  which  may  be  termed  dir  ell 
ocular  fpedtra.  4th.  Such  as  are  of  a colour  contrary  to  that 
of  their  objedt,  which  may  be  termed  reverfe  ocular  fpedtra. 

The  laws  of  light  have  been  moft  fuccefslully  explained  by 
the  great  Newton,  and  the  perception  of  vifible  objects  lias 
been  ably  inveftigated  by  the  ingenious  Dr;  Berkeley  and  M. 
Malebranche;  but  thefe  minute  phenomena  of  vifion  have  yet 
been  thought  reducible  to  no  theory,  though  many  philolophers 
have  employed  a confiderable  degree  of  attention  upon  them  : 
among  thefe  are,  Dr.  Jurin,  at  the  end  of  Dr.  Smith’s  Optics; 
M.  ALpinus,  in  the  Nov.  Cora.  Petropol.  vol.  x.  M.  Beguelin, 
in  the  Berlin  Memoires,  vol.  ii.  1 7 7 1 ; M.  d’Arcy,  in  the  Hiftorie 
de  l’Acad.  des  Scienc.  1765  ; M.  de  la  Hire ; and,  laftly,  the  ce- 
lebrated M.  de  Buffon,  in  the  Memoirs  de  l’Acad.  des  Scienc. 
who  has  termed  them  accidental  colours,  as  if  fubjedted  to  no 
eftablithed  laws.  Ac.  Par.  1743.  M.  p.215. 

I mull;  here  apprize  the  reader,  that  it  is  very  difficult  for  dif- 
ferent people  to  give  the  fame  names  to  various  tirades  of  colours; 
whence,  in  the  following  pages,  fomething  muft  be  allowed,  if, 
on  repeating  the  experiments,  the  colours  here  mentioned  tliould 
not  accurately  correfpond  with  his  own  names  of  them. 


I.  Activity  of  the  Retina  in  Rif  on. 

From  the  fubfequent  experiments  it  appears,  that  the  retina 
is  in  an  adtive,  not  in  a paffive  ftate,  during  the  exiftence  of 
thefe  ocular  fpedtra ; and  it  is  thence  to  be  concluded,  that  all 
vifion  is  owing  to  the  adtivity  of  this  organ. 

X.  Place  a piece  of  red  filk,  about  an  inch  in  diameter,  as  in 
plate  1,  at  Sedt.  III.  1.  on  a theet  of  white  paper,  in  a ftrong 
light;  look  fteadily  upon  it,  from  about  the  diftance  of  half  a 
yard,  for  a minute  ; then  clofing  your  eye-lids,  cover  them  with 
your  hands,  and  a green  fpedtrum  will  be  feen  in  your  eyes, 
refembling  in  form  the  piece  of  red  filk  ; after  fome  time  this 
fpedtrum  will  difappear,  and  fhortly  re-appear;  and  this  alter- 
nately three  or  four  times,  if  the  experiment  is  well  made,  till 
at  length  it  vanifhes  entirely. 

2.  Place  on  a fheet  of  white  paper,  a circular  piece  of  blue 
filk,  about  four  inches  in  diameter,  in  the  funthine;  cover  the 

F f f center 


OCULAR  SPECTRA. 


Sect.  XL.  r. 


396 

center  of  this  with  a circular  piece  of  yellow  filk,  about  three 
inches  in  diameter;  and  the  center  of  the  yellow  filk  with  a 
circle  of  pink  filk,  about  two  inches  in  diameter ; and  the  center 
of  the  pink  filk  with  a circle  of  green  filk,  about  one  inch  in 
diameter;  and  the  center  of  this  with  a circle  of  indigo,  about 
half  an  inch  in  diameter;  make  a fmall  fpeck  with  ink  in  the 
very  center  of  the  whole,  as  in  plate  3.  at  Se£t.  III.  3.  6.  look 
fteadily  for  a minute  on  this  cential  fpot,  and  then  clofing  your 
eyes,  and  apply  your  hand  at  about  an  inch  diftance  before 
them,  fo  as  to  prevent  too  much  or  too  little  light  from  palling 
through  the  eye-lids,  you  will  fee  the  mod  beautiful  circles  of 
colours  that  imagination  can  conceiveT  which  are  moll:  re- 
fembied  by  the  colours  occafioned  by  pouring  a drop  or  two 
of  oil  on  a dill  lake  in  a bright  day  ; but  thefe  circular  irifes  of 
colours  are  not  only  different  from  the  colours  of  the  filks 
above  mentioned,  but  are,  at  the  fame  time,  perpetually  chang- 
ing as  long  as  they  exifl. 

3.  When  any  one  in  the  dark  preffes  either  corner  of  his 
eye  with  his  finger,  and  turns  his  eye  away  from  his  finger,  lie 
will  fee  a circle  of  colours  like  thofe  in  a peacock’s  tail;  anil 
a fudden  flafh  of  light  is  excited  in  the  eye  by  a ftroke  on  it. 
Newton’s  Opt.  16. 

4.  When  any  one  turns  round  rapidly  on  one  foot,  till  he 
becomes  dizzy,  and  falls  upon  the  ground,  the  ipedtra  of  the 
ambient  objedls  continue  to  prefent  themfelves  in  rotation,  or 
appear  to  iibrate,  and  he  leeras  to  behold  them  for  fome  time 
ftill  in  motion. 

From  all  thefe  experiments  it  appears,  that  the  fpeefra  in  the 
eye  are  not  owing  to  the  mechanical  impulfe  of  light  impreffed 
on  the  retina,  nor  to  its  chemical  combination  with  that  organ, 
nortothe  abforptionandemiffion  of  light, as  is  obferved  in  many 
bodies ; for  in  all  thefe  cafes  the  fpedlra  muff  either  remain 
uniformly,  or  gradually  dimini fh ; and  neither  their  alternate 
prefence  and  evanefcence,  as  in  the  firft  experiment ; nor  the 
perpetual  changes  of  their  colours,  as  in  the  fecond;  nor  the  flafh 
of  light  or  colours  in  the  preffed  eye,  as  in  the  third ; nor  the  ro- 
tation or  iibration  of  the  lpedtra,  as  in  the  fourth,  could  exift. 

It  is  not  ablurd  to  conceive,  that  the  retina  may  be  ftimulat- 
ed  into  motion,  as  w'ell  as  the  red  and  white  mufcles  which 
form  our  limbs  and  veffels,  fince  it  confifts  of  fibres,  like  thofe 
intermixed  with  its  medullary  fubftance.  To  evince  this  ftruc- 
ture,  the  retina  of  an  ox’s  eye  was  fufpended  in  a glafs  of  warm 
water,  and  forcibly  torn  in  a few  places;  the  edges  of  thele 
parts  appeared  jagged  and  hairy,  and  did  not  contract,  and 
become  irnootn  like  fimpie  mucus,  when  it  is  diftended  till  it 

breaks ; 


Sect.  XL.  2, 


OCULAR  SPECTRA. 


397 

tbreaks  ; which  {hews 'that  it  confifts  of  fibres;  and  this,  its 
fibrous  conftrudion,  became  ftill  more  diftind  to  the  fight,  by- 
adding  fomecauftic  alkali  to  the  water,  as  the  adhering  mucus 
was  firft  eroded,  and  the  hair-like  fibres  remained  floating  in 
the  veflfel.  Nor  does  the  degree  of  tranfparency  of  the  retina 
invalidate  the  evidence  of  its  fibrous  ftrudure,  fince  Leeu- 
wenhoek has  fhewn  that  the  cryftalline  humour  itfelf  confifts 
of  fibres.  Arcana  Naturae,  vol.  i.  p.  70. 

Hence  it  appears,  that  as  the  mufcles  have  larger  fibres  in- 
termixed with  a fmaller  quantity  of  nervous  medulla,  the  organ 
of  vifion  has  a greater  quantity  of  nervous  medulla  intermixed 
-with  fmaller  ,fibres;  and  it  is  probable  that  the  locomotive  muf- 
cles, qs  well  as  the  vafcular  ones,  of  microfcopic  animals,  have 
much  greater  tenuity  than  thefe  of  the  retina. 

And  befides  the  iimilar  laws,  which  will  be  fhewn  in  this 
paper  to  govern  alike  the  adions  of  the  retina  and  of  the  muf- 
cles, there  are  many,  other  analogies  which  exift  between  them. 
They  are  both  originally  excited  into  action  by  irritations, 
-both  add  nearly  in  the  fame  quantity  of  time,  are  alike  ftrength- 
-ened  or  fatigued  by  exertion,  are  alike  painful  if  excited  into 
• adfion  when  they  are  in  an  inflamed  ftate,  are  alike  liable  to 
jraralyfis,  and  to  the. torpor, of  old  age. 

II.  QfSpelira  from  Defeat  of  SenfbiUty. 

The  retina  is  not  fo  eafily  excited  into  adtion  by  lefs  irritation 
after  having  been  lately  fubjefled  to  greater. 

1.  When  any  one  pafles  from  the  bright  day-light  into  a 
•darkened  room,  the  irifes  of  his  eyes  expand  themfelves  to  their 
'Utmoft  extent  in  a few  feconds  of  time  ; but  it  is  very  long  be- 
fore the  optic  nerve,  after  having  been  ftimulated  by  the  greater 
•light  of  the  day,  becomes  fenfibie  of  the  lefs  degree  of  it  in  the 
room  ; and,  if  the  room  is  not  loo  obfcure,  the  irifes  will  again 
contrad  themfelves  in  fome  degree,  as  the  fenfibility  of  the 
retina  returns. 

2.  Place  about  half  an  inchfquare  of  white  paper  on  a black 
hat,  and,  looking  fteadily  on  the  center  of  it  tor  a minute,  remove 
your  eyes  to  a {fleet  of  white  paper ; and  after  a fecond  or  two 
a dark  fquare  will  be  feen  on  the  white  paper,  which  will  con- 
tinue fome  time.  A fimilar  dark  fquare  v/ill  be  feen  in  the 
doled  eye,  if  light  be  admitted  through  the  eye-lids. 

So  after  looking  at  any  luminous  objed  of  a fmall  fize,  as 
at  the  fun,  for  a fhort  time,  fo  as  not  much  to  fatigue  the  eyes, 
■this  part  of  the  retina  becomes  lefs  fenfibie  to  fmaller  quantities 
of  light ; hence,  when  the  eyes  are  turned  on  other  lefs  luminous 
Hearts  of  the  Iky,  a dark  fpot  is  feen  refembling  the  fhape  of  the 

fiWb 


OCULAR  SPECTRA. 


Sect.XL.  E 


398 

fun,  or  other  luminous  object  which  we  lafl:  beheld.  This 
is  the  fource  of  one  kind  of  the  dark-coloured  mu  Jets  volitantes. 
If  this  dark  fpot  lies  above  the  center  of  the  eye,  we  turn  our 
eyes  that  way,  expecting  to  bring  it  into  the  center  of  the  eve, 
that  w'e  may  view  it  more  diftincfly;  and  in  this  cafe  the  dark 
fpedbrum  feems  to  move  upwards.  If- the  dark  fpedlrum  is 
found  beneath  the  center  ot  the  eye,  we  purfue  it  from  the  fame 
motive,  and  it  feems  to  move  downwards.  This  has  given 
l ife  to  various  conjectures  of  fomething  floating  in  the  aqueous 
humours  of  the  eyes;  but  whoever,  in  attending  to  thefe  fpots, 
keeps  his  eyes  unmoved,  by  looking  fteadily  at  the  corner  of 
a cloud,  at  the  fame  time  that  he  obferves  the  dark  fpedtra, 
will  be  thoroughly  convinced,  that  they  have  no  motion  but 
what  is  given  to  them  by  the  movement  of  our  eyes  in  puriuit 
of  them.  Sometimes  the  form  of  the  fpeCtrum,  when  it  has 
been  received  from  a circular  luminous  body,  will  become 
oblong;  and  fometimes  it  will  be  divided  into  two  circular 
fpedlra,  which  is  not  owing  to  our  changing  the  angle  made 
by  the  two  optic  axiles,  according  to  the  diftance  of  the  clcud 
or  other  bodies  to  which  the  fpectrum  is  fuppofed  to  be  conti  - 
guous, but  to  other  caufes,  mentioned  in  No.  X.  3.  of  tin’s 
feCfion.  The  apparent  fize  of  it  will  alfo  be  variable  according 
to  its  fuppofed  diftance. 

As  thefe  fpedtra  are  more  eaftly  cbfervable  when  our  eyes 
are  a little  weakened  by  fatigue,  it  has  frequently  happened, 
that  people  of  delicate  conltitutions  have  been  much  alarmed 
at  them,  fearing  a beginning  decay  of  their  light,  and  have 
thence  fallen  into  die  hands  of  ignorant  oculifts  ; but  I believe 
they  never  arc  a prelude  to  any  other  difeafe  of  the  eye,  and 
that  it  is  from  habit  alone,  and  our  want  of  attention  to  them, 
that  we  do  not  lee  them  on  all  objects  every  hour  of  our  lives. 
But  as  the  nerves  of  very  weak  people  lofe  their  fenlibility,  in 
the  fame  manner  as  their  mufcles  lofe  their  activity,  by  a fmali 
time  of  exertion,  it  frequently  happens,  diat  lick  people,  in  the 
extreme  debility  of  fevers,  are  perpetually  employed  in  picking 
fomething  from  the  bed-clothes,  occationed  by  their  miftaking 
the  appearance  of  thefe  mtzfcee  vohtantes  in  their  eyes.  Ben- 
venuto Ceiini,  an  Italian  artift,  a man  of  llrong  abilities,  re- 
lates, that  having  pa-fled  die  whole  night  on  a diltant  mountain 
with  fome  companion^and  a conjurer,  and  pertormed  manv 
ceremonies  to  raife  the  devil,  on  their  return  in  the  morning 
to  Rome,  and  looking  up  when  the  fun  began  to  rife,  they  faw 
numerous  devils  run  on  the  tops  of  the  houies,  as  they  pafleti 
along;  fo  much  weie  tire  fpedtra  of  their  weakened  eyes  mag- 
nified by  fear,  and  made  fubfervient  to  the  puTpofes  ot  fraud  or 
fuperftition.  (Life  of  Ben.  Ceiini.) 

3.  Place 


OCULAR  SPECTRA. 


Sect.  XL.  3. 


399 


3.  Place  a fquare  inch  of  white  paper  on  a large  piece  of 
ftraw-coloured  filk ; look  fteadily  fome  time  on  the  white  paper, 
and  then  move  the  center  of  your  eyes  on  the  filk,  and  a fpedftrum 
of  the  form  of  the  paper  will  appear  on  the  filk,  of  a deeper 
yellow  than  the  other  part  of  it:  for  the  central  part  of  the 
retina  having  been  fome  time  expofed  to  the  ftimulus  of  a greater 
quantity  of  white  light,  is  become  lefs  fenfible  to  a fmaller 
quantity  of  it,  and  therefore  fees  only  the  yellow  rays  in  that 
part  of  the  ftraw-coloured  filk. 

Fadfs  fimilar  to  thefe  are  obfervable  in  other  parts  of  our 
fvftem : thus,  if  one  hand  be  made  warm,  and  the  other  ex- 
pofed to  the  cold,  and  then  both  of  them  immerfed  in  fubtepid 
water,  the  water  is  perceived  warm  to  one  hand,  and  cold  to 
die  other  ; and  we  are  not  able  to  hear  weak  founds  for  fome 
time  after  we  have  been  expofed  to  loud  ones  ; and  we  feel  a 
chillinefs  on  coming  into  an  atmofphere  of  temperate  warmth, 
after  having  been  fome  time  confined  in  a very  warm  room: 
and  hence  the  ftomach,  and  other  organs  of  digeftion,  of  thofe 
who  have  been  habituated  to  the  greater  ftimulus  of  fpirituous 
liquor,  are  not  excited  into  their  due  adlion  by  the  lefs  ftimulus 
of  common  food  alone ; of  which  the  immediate  confequence 
is  indigeftion  and  hypochondriacifm. 

TIL  Of  Speflra  from  Exeefs  of  Senfi bility. 

The  retina  is  more  eajily  excited  into  aftion  by  greater  irri- 

' tation  after  having  been  lately  fubjefled  to  lefs. 

1.  If  the  eyes  are  clofed,  and  covered  perfefilly  with  a hat, 
for  a minute  or  two,  in  a bright  day,  on  removing  the  hat  a red 
or  crimfon  light  is  feen  through  the  eye-lids.  In  this  experiment 
the  retina,  after  being  fome  time  kept  in  the  dark,  becomes  fo 
fenfible  to  a fmall  quantity  of  light,  as  to  perceive  diftindlly  the 
greater  quantity  of  red  rays  than  of  others  which  pafs  through 
the  eye- lids.  A fimilar  coloured  light  is  feen  to  pafs  through 
the  edge-s  of  the  fingers,  when  the  open  hand  is  oppofed  to  the 
flame  of  a candle. 

2.  If  you  look  for  fome  minutes  fteadily  on  a window  in  the 
beginning  of  the  evening  twilight,  or  in  a dark  day,  and  then 
move  your  eyes  a little,  fo  that  thofe  parts  of  the  retina  on 
which  the  dark  frame-workof  the  window  was  delineated,  may 
now  fall  on  the  glafs  part  of  it,  many  luminous  lines,  repre- 
fenting  the  frame-work,  will  appear  to  lie  acrois  the  glafs  panes ; 
dor  thofe  parts  of  the  retina  which  were  before  leaft  ftimulared 
by  the  dark  frame-work,  are  now  more  fenfible  to  light  than 
the  other  parts  of  the  retina  which  were  expofed  to  the  more 
luminous  parts  of*the  window. 


3.  Make 


400 


OCULAR  SPECTRA. 


Sect.  XL.  3. 

3.  Make  with  ink,  on  white  paper,  a very  black  fpot,  about 
halt  an  inch  in  diameter,  with  a tail  about  an  inch  in  length,  fo 
as  to  reprefent  a tadpole,  as  in  plate  2.  at  Se£t.  III.  8.  3.  look 
Readily  lor  a minute  on  this  fpot,  and,  on  moving  the  eye  a 
little,  the  figure  of  the  tadpole  will  be  feen  on  the  white  part  of 
the  paper ; which  figure  of  the  tadpole  will  appear  whiter  or 
more  luminous  than  the  other  partset  the  white  paper  ; for  the 
part  of  the  retina  an  which  the  tadpole  was  delineated,  is  now 
more  fenlible  to  light  than  the  other  parts  of  it,  which  were  ex- 
pofed  to  the  white  paper.  This  experiment  is  mentioned  by 
J)r.  Irwin,  but  is  not  by  him  afcribed  to  the  truecaufe,  namely, 
the  greater  fenfibility  of  that  part  of  the  retina  which  has  been 
expofed  to  the  black  fpot,  than  of  the  other  parts  which  had  re- 
ceived the  white  field  of  paper,  which  is  put  beyond  a doubt  by 
the  next  experiment. 

4.  On  doling  the  eyes,  after  viewing  the  black  fpot  on  the 
white  paper,  as  in  the  foregoing  experiment,  a red  fpot  is  feen 
of  the  form  of  the  black  fpot;  for  that  part  of  the  retina  on 
which  the  black  fpot  w'as  delineated,  being  now  more  fenfible 
to  light  than  the  other  parrs  of  it,  which  were  expofed  to  die 
white  paper,  is  capable  of  perceiving  the  red  rays  which  pene- 
trate the  eye-lids.  If  this  experiment  be  made  by  the  light  of  a 
tallow  candle,  the  fpot  will  be  yellow  inftead  of  red;  tor  tallow 
candles  abound  much  with  yellow  light,  which  pafles  in  greater 
quantity  and  force  through  the  eye-lids  than  blue  light:  hence 
the  difficulty  of  diffinguifhing  blue  and  green  by  this  kind  of 
candle-light.  The  colour  of  the  fpedrum  may  poffiblv  vary 
in  the  day-light,  according  to  the  different  colour  of  the  meri- 
dian, or  the  morning  or  evening  light. 

M.  Beguelin,  in  the  Berlin  Memoires,  vol.  ii.  1771,  obferves, 
that,  when  lie  held  a book  fo  that  thfe  fun  fhone  upon  his  halt- 
ed ofed  eye-lids,  the  black  letters,  which  he  had  long  infpedlcd, 
became  red,  which  muff  have  been  thus  occafioned.  Thofe 
parts  of  the  retina  which  had  received,  for  fome  time,  the  black 
letters,  were  fo  much  more  fenfible  than  thofe  parts  which  had 
been  oppofed  to  the  white  paper,  that  to  the  former  the  red  light 
w hich  paffed  through  the  eye-lids  was  perceptible.  There  is  a 
fimilar  ftory  told,  I think,  in  M.  de  Voltaire’s  hifiorical  works,  of 
a duke  of  Tufcany,  who  wms  playing  at  dice  with  the  general  of 
'a  foreign  army,  and,  believing  he  faw  bloody  fpots  upon  the 
dice,  portended  dreadful  events,  and  retired  in  confufion.  The 
obferver,  after  looking  for  a minute  on  the  black  fpors  of  a die, 
and  carelefsly  doling  bis  eyes,  on  a bright  day,  would  lee  the 
image  of  a die  wfith  red  fpots  upon  it,  as  above  explained. 

5.  On  emerging  from  a dark  cavern,  where  we  have  long 

continued. 


Sect.  XL.  3,  OCULAR  SPECTRA,  40  r 

continued,  the  light  of  a bright  day  becomes  intolerable  to  the 
eye  for  a confiderable  time,  owing  to  the  excefs  of  fenCbility 
exiting  in  the  eye,  after  having  been  long  expos’d  to  little  or 
no  ftimulus.  This  occafions  us  immediately  to  contract  the 
iris  to  its  fmalleft  aperture,  which  becomes  again  gradually  di- 
lated, as  the  retina  becomes  accuftomed  to  the  greater  ftimulus 
of  the  day-light. 

The  twinkling  of  a bright  ftar,  or  of  a diftant  candle,  in  the 
night,  is  perhaps  owing  to  the  fame  caufe-  While  we  continue 
to  look  upon  thefe  luminous  objects,  their  central  parts  gra- 
dually appear  paler,  owing  to  the  decreafmg  fenfibility  of  the 
part  of  the  retina  expofed  to  their  light ; whilft,  at, the  fame 
time,  by  the  unfteadinefs  of  the  eye,  the  edges  of  them  are  per- 
petually falling  on  parts  of  the  retina,  that  were  juft  before  ex- 
pofed to  the  darknefs  of  the  night,  and  therefore  tenfold  more 
fenfible  to  light  than  the  part  on  which  the  ftar  or  candle  had 
been  for  fome  time  delineated.  This  pains  the  eye  in  afimilar 
manner  as  when  we  come  fuddenly  from  a dark  room  into 
bright  day-light,  and  gives  the  appearance  of  bright  fcintillations. 
Hence  the  ftars  twinkle  moft  when  the  night  is  darkeft,  and  do 
not  twinkle  through  telefcopes,  as  obferved  by  Mufichenbroeck ; 
and  it  will  afterwards  be  leen  why  this  twinkling  is  fometimes 
of  different  colours,  when  the  objedf  is  very  bright,  as  Mr.  Mel- 
vill  obferved  in  looking  at  Sirius.  For  the  opinions  of  others 
on  this  fubjedl,  fee  Dr.  Prieftley’s  valuable  Hiftory  of  Light 
and  Colours,  p.  494. 

Many  fails  obfervable  in  the  animal  fyftem  are  ftmilar  to 
thefe ; as  the  hot  glow  occaftoned  by  the  ufual  warmth  of  the 
air,  or  our  clothes,  on  coming  out  of  a cold  bath  ; the  pain  of 
the  fingers,  on  approaching  the  fire  after  having  handled  fnow ; 
and  the  inflamed  heels  from  walking  in  fnow.  Hence  thofe 
who  have  been  expofed  to  much  cold,  have  died  on  being 
brought  to  a fire,  or  their  limbs  have  become  fo  much  inflamed 
as  to  mortify.  Hence  much  food  or  wine,  given  fuddenly  to 
thofe  who  have  almoft  perifhed  by  hunger,  has  deftroyed  them ; 
fot  all  the  organs  of  the  famifhed  body  are  now  become  fo 
much  more  irritable  to  the  ftimulus  of  food  and  wine,  which 
they  have  long  been  deprived  of,  that  inflammation  is  excited, 
which  terminates  in  gangrene  or  fever. 


TV.  Of 


402 


OCULAR  SPECTRA.  Sect.  XL.  4. 

IV.  Of  dire  ft  Ocular  Spedlra. 

A quantity  of  fiimulus  fomewhat  greater  than  natural  excites 

the  retina  into  fpafmodic  aflion,  which  ceafes  in  a few 

fcconds. 

A certain  duration  and  energy  of  the  ftimulus  of  light 
and  colours  excites  the  perfect  action  of  the  retina  in  vifion ; 
for  very  quick  motions  are  imperceptible  to  us,  as  well  as  very 
flow  ones,  as  the  whirling  of  a top,  or  the  lhadow  on  a fun- 
dial.  So  perfedt  darknefs  does  not  affedt  the  eve  at  all ; and 
excefs  of  light  produces  pain,  not  vifion. 

1.  When  a fire-coal  is  whirled  round  in  the  dark,  a lucid 
circle  remains  a confiderable  time  in  the  eye  ; and  that  with  fo 
much  vivacity  of  light,  that  it  is  miftaken  for  a continuance 
of  the  irritation  of  the  object.  In  the  fame  manner,  when  a 
fiery  meteor  fhoots  acrofs  the  night,  it  appears  to  leave  a long 
lucid  train  behind  it,  part  of  which,  and  perhaps  fometimes  the 
whole,  is  owing  to  the  continuance  oi  the  adtion  of  the  retina 
after  having  been  thus  vividly  excited.  This  is  beautifully 
illuftrated  by  the  following  experiment:  Fix  a paper  fail,  three 
or  four  inches  in  diameter,  and  made  like  that  of  a fmoak-jack, 
in  a tube  of  pafteboard ; on  looking  through  the  tube  at  a dif- 
tant  profpedt,  fome  disjointed  parts  of  it  will  be  fee.n  through  the 
narrow  intervals  between  the  fails ; but  as  the  fly  begins  to 
revolve,  tbefe  intervals  appear  larger;  and  when  it  revolves 
quicker,  the  whole  profpedt  is  feen  quite  as  diftindt  as  if  no- 
thing intervened,  though  lefs  luminous. 

2.  Look  through  a dark  tube,  about  half  a yard  long,  at 
the  area  of  a yellow  circle  of  half  an  inch  diameter,  lying  upon 
a blue  area  of  double  that  diameter,  for  half  a minute ; and,  on 
clofing  your  eyes,  the  colours  of  the  fpedtrum  will  appear  fimi- 
lar  to  the  two  areas,  as  in  fig.  3. ; but  if  the  eye  is  kept  too 
long  upon  them,  the  colours  of  the  fpedtrum  will  be  the  reverie 
of  thofe  upon  the  paper ; that  is,  the  internal  circle  will  become 
blue,  and  the  external  area  veliow : hence  fome  attention  is 
required  in  making  this  experiment. 

3.  Place  the  bright  flame  of  a fpermaceti  candle  before  a 
black  object  in  the  night;  look  fteadily  at  it  lor  a fhort  time, 
till  it  is  obferved  to  become  fomewhat  paler;  and,  on  clofing 
the  eyes,  and  covering  them  carefully,  but  not  lo  as  to  coinprefs 
them,  the  image  of  the  blazing  candle  will  continue  diflindtly 
to  be  vifible. 

4.  Look  fleadilv,  for  a fhort  time,  at  a window  in  a dark 
day,  as  in  Exp.  2.  Sect.  III.  and  then  clofing  your  eyes,  and 

covering 


OCULAR  SPECTRA. 


Sect.  XL.  5. 


40S 


covering  them  with  your  hands,  an  exad  delineation  of  the 
window  remains  for  fome  time  vifible  in  the  eye.  This  expe- 
riment requires  a little  ptadice  to  make  it  fucceed  well ; fince, 
if  the  eyes  are  fatigued  by  looking  too  long  on  the  window,  or 
the  day  be  too  bright,  the  luminous  parts  of  the  window  will 
appear  dark  in  the  fpedrum,  and  the  dark  parts  of  the  frame- 
work will  appear  luminous,  as  in  Exp.  2.  Sed.  III.  And  it 
is  even  difficult  for  many,  who  firft  try  this  experiment,  to 
perceive  the  fpedrum  at  all;  for  any  hurry  of  mind,  or  even 
too  great  attention  to  the  fpedrum  itfelf,  will  difappoint  them, 
till  they  have  had  a little  experience  in  attending  to  fuch  fmali 
-fenfations. 

The  fpedra  defcribed  in  this  fedion,  termed  direct  ocular 
fpedra,  are  produced  without  much  fatigue  of  the  eye;  the 
irritation  of  the  luminous  object  being  foon  withdrawn,  on  its 
^quantity  of  light  being  not  fo  great  as  to  produce  any  degree  of 
.uneafinefs  in  the  organ  of  vifion ; which  diftinguilhes  them 
from  the  next  clafs  of  ocular  fpedra,  which  are  the  confequence 
of  fatigue.  Thefe  dired  fpedra  are  beft  obferved  in  fuch  cir- 
.cumftances,  that  no  light,  but  what  comes  from  the  object,  can 
fall  upon  the  eye;  as  in  looking  through  a tube,  of  half  a yard 
long,  and  an  inch  wide,  at  a yellow  paper  on  the  fide  of  a 
room,  the  dired  fpedrum  was  eafily  produced  on  doling  the 
eye  without  taking  it  from  the  tube : but  if  the  lateral  light  is 
admitted  through  the  eye -lids,  or  by  throwing  the  fpedrum  ou 
white  paper,  it  becomes  a reverfe  fpedrum,  as  wrill  be  explain- 
ed below. 

The  other  fenfes  alfo  retain  for  a time  the  impreffions  that 
have  been  made  upon  them,  or  the  adions  they  have  been  ex- 
eited  into.  So,  if  a 'hard  body  is  prelfed  upon  the  palm  of  the 
hand,  as  is  pradifed  in  tricks  of  legerdemain,  it  is  not  eafy  to 
diftinguifh  for  a few  feconds,  whether  it  remains  or  is  remov- 
ed; and  taftes  continue  long  to  exifi:  vividly  in  the  mouth,  as 
the  fmoke  of  tobacco,  or  the  tafte  of  gentian,  after  the  fapid 
material  is  withdrawn. 

V.  A quantity  of  fiimuhts  fomewhat  greater  than  the  laji 

mentioned. , excites  the  retina  into  fpafmodic  aciion,  winch 

ceafes  and  recurs  alternately. 

1.  On  looking  for  a time  on  the  fetting  fun,  fo  as  not  greatly 
to  fatigue  the  fight,  a yellow  fpedrum  is  feen  when  the  eyes 
are  clofed  and  covered,  which  continues  for  a time,  and  then 
difappears,  and  recurs  repeatedly  before  it  entirely  vanilhes. 
This  yellow  fpedrum  of  the  fun,  when  the  eye-lids  are  opened, 
becomes  blue ; and  if  it  is  made  to  fall  on  the  green  grafs,  or 

on 


40A  OCULAR  SPECTRA.  Sect.  XL.  6. 

on  other  coloured  objedts,  it  varies  its  own  colour  bv  an  inter- 
mixture of  theirs,  as  will  be  explained  in  another  place. 

2.  Piace  a lighted  fpermaceti  candle,  in  the  night,  about  one 
foot  from  your  eye,  and  look  fteadily  on  the  center  of  the  flame, 
till  your  eye  becomes  much  more  fatigued  than  in  Sedt.  IV. 
Exp.  3.  and  on  doling  your  eyes,  a reddifh  fpedtrum  will  be 
perceived,  which  will  ceafe  and  return  alternately. 

The  adtion  of  vomiting  in  like  manner  ceafes,  and  is  re- 
newed by  intervals,  although  the  emetic  drug  is  thrown  up  with 
the  firft  effort:  fo  after-pains  continue  fomc  time  after  partu- 
rition ; and  the  alternate  pulfations  of  the  heart  of  a viper  are 
renewed  for  fome  time  after  it  is  cleared  from  its  blood. 

VI.  Of  reverfe  Ocular  Spcdira. 

The  retina , after  having  been  excited  into  action  by  a ftimu- 

Ius  fornevjhat  greater  than  the  laf  mentioned , falls  into 

oppojite  fpafmodic  adtion. 

The  adtions  of  every  part  of  animal  bodies  may  be  advan- 
tageoufly  compared  witli  each  other.  This  ftridt  analogy  con- 
tributes much  to  the  inveftigation  of  truth;  while  thole  loofer 
analogies,  which  compare  the  phenomena  of  animal  life  with 
thofe  of  chemiftry  or  mechanics,  only  ferve  to  miflead  our  in- 
quiries. 

When  any  of  our  larger  mufcles  have  been  in  long,  or  in 
violent  adticn,  and  their  antogonifts  have  been  at  the  fame  time 
extended,  as  foon  as  the  action  of  the  former  ceafes,  the  limb 
is  flretched  the  contrary  way  for  our  eafe,  and  a pandiculation 
or  yawning  takes  place. 

By  the  following  oblervations  it  appears,  that  a fimilar  cir- 
cumftance  obtains  in  the  organ  of  vifiof) : after  it  has  been 
fatigued  by  one  kind  of  action,  it  fpontaneoufly  falls  into  the 
oppolite  kind. 

1.  Place  a piece  of  coloured  filk,  about  an  inch  in  diameter, 
on  a fheet  of  white  paper,  about  half  a yard  from  your  eyes; 
look  fteadily  upon  it  lor  a minute , then  remove  your  eyes  upon 
another  part  of  the  white  paper,  and  a fpedtrum  will  be  feen 
of  the  form  of  the  filk  thus  infpedled,  but  of  a colour  oppolite 
to  it.  A fpedtrum  nearly  fimilar  will  appear  if  the  eyes  are 
clofed,  and  the  eve-lids  fhaded  by  approaching  the  hand  near 
them,  fo  as  to  permit  fome,  but  to  prevent  too  much  light  fall- 
rug  on  them. 

Red  filk  produced  a green  fpedtrum. 

Green  produced  a red  one. 

Orange  produced  blue. 

B!ue  P1 oduced  orange. 

' . ' Yellow 


OCULAR  SPECTRA. 


Ssct.XL.  6. 


4°S 


Yellow  produced  violet. 

Violet  produced  yellow. 

That  in  thefe  experiments  the  colours  of  the  fpedra  are  the 
reverfe  of  the  colours  which  occafioned  them,  may  be  feenby 
^examining  the  third  figure  in  Sir  Ifaac  Newton’s  Optics,  L. 

11.  p.  1.  where  thofe  thin  laminae  of  air,  which  reflected  yellow, 
franfmitted  violet;  thofe  which  reflected  red,  tranfmitted  a blue- 
green  ; and  fo  or  the  reft,  agreeing  with  the  experiments  above 
related. 

1.  Thefe  reverfe  fpedra  are  fimilar  to  a colour,  formed  by 
a combination  of  all  the  primary  colours,  except  that  with  which 
the  eye  has  been  fatigued  in  making  the  experiment : thus  the 
reverfe  fpedrum  of  red  muft  be  fuch  a green  as  would  be  pro- 
duced by  a combination  of  all  the  other  prifmatic  colours.  To 
evince  this  fad,  the  following  fatisfadory  experiment  was 
made.  The  prifmatic  colours  were  laid  on  a circular  pafte- 
board  wheel,  about  four  inches  in  diameter,  in  the  proportions 
defcribed  in  Dr.  Prieftley’s  Hiftory  of  Light  and  Colours,  pi. 

12.  fig.  83.  except  that  the  red  compartment  was  entirely  left 
out,  and  die  others  proportionably  extended  fo  as  to  complete 
the  circle.  Then,  as  the  orange  is  a mixture  of  red  and  yellow, 
and  as  the  violet  is  a mixture  of  red  and  indigo,  it  became  ne- 
ceftary  to  put  yellow  011  the  wheel  inftead  of  orange,  and  in- 
digo inftead  of  violet,  that  the  experiment  might  more  exadly 
quadrate  with  the  theory  it  was  defigned  to  eftablilh  or  con- 
fute; becaufe,  in  gaining  a green  fpedrum  from  a red  objed, 
the  eye  is  fuppoled  to  have  become  infenfible  to  red  light.  This 
wheel,  by  means  of  an  axis,  was  made  to  whirl  like  a top ; 
and  on  its  being  put  in  motion,  a green  colour  was  produced, 
correfponding  with  great  exadnefs  to  the  reverfe  fpedrum  of 
red. 

3.  In  contemplating  any  one  of  thefe  reverfe  fpedra  in  the 
doled  and  covered  eye,  it  difappears  and  re-appears  feveral 
times  fucceffively,  till  at  length  it  entirely  vanilhes,  like  the 
dired  fpedra  in  Sed . V. ; but  with  this  additional  circurnftance, 
that  when  the  fpedrum  becomes  faint  or  evanefcent,  it  is  in- 
ftantly  revived  by  removing  the  hand  from  before  the  eye-lids,  fo 
as  to  admit  more  light:  becaufe  then  not  only  the  fatigued  part 
of  the  retina  is  inclined  fpontaneoufly  to  fall  into  motions  of  a 
contrary  diredion,  but  being  ftill  fenfible  to  all  other  rays  of 
light,  except  that  with  which  it  was  lately  fatigued,  is,  by  thefe 
rays,  at  the  fame  time  ftimuiated  into  thofe  motions  which  form 
the  reverfe  fpedrum. 

From  thefe  experiments  there  is  reafon  to  conclude,  that  the 
fatigued  part  of  the  retina  throws  itfelf  into  a contrary  mode  of 

adion, 


OCULAR  SPECTRA. 


406 


Sect.XL.7. 


a£tion,  like  ofcitation  or  pandiculation,  as  foon  as  the  ftimulus 
which  has  fatigued  it  is  withdrawn ; and  that  it  ftiil  remains 
fenfible;  that  is,  liable  to  be  excited  into  action  by  any  other 
colours  at  the  fame  time,  except  the  colour  with  which  it  has 
been  fatigued. 


VII.  The  retina , after  having  been  excited  into  action  by  a 

Jilmulus  fomewhat  greater  than  the  lajl  mentioned , fallt 

Into  various  fuccejjive  fpafmodic  actions. 

1.  On  looking  at  the  meridian  fun  as  long  as  the  eyes  can 
well  bear  its  brightnefs,  the  di£k  firft  becomes  pale,  with  a lu- 
minous crefcent,  which  feems  to  librate  from  one  edge  of  it  to 
the  other,  owing  to  the  unheadinefs  of  the  eye  ; then  the  whole 
phafis  of  the  fun  becomes  blue,  furrounded  with  a white  halo  ; 
and  on  clofing  the  eyes,  and  covering  them  with  the  hands,  a 
yellow  fpedtrum  js  feen,  which,  in  a little  time,  changes  into 
a blue  one. 

M.  de  la  Hire  obferved,  after  looking  at  the  bright  fun,  that 
the  impreffion  in  his  eye  firft  affumed  a yellow  appearance, 
and  then  green,  and  then  blue;  and  wifhes  to  aferibe  thefe  ap- 
pearances to  fome  affection  of  die  nerves.  Porterfield  on  the 
Eye,  vol.  i.  p.  343. 

2.  After  looking  fteadily'  on  about  an  inch  fquare  of  pink 
filk,  placed  on  white  paper,  in  a bright  funfhine,  at  die  di  ft  a nee 
of  a foot  from  my  eyes,  and  doling  and  covering  mv  eye-iids, 
the  fpedlrum  of  the  fiik  was  at  firft  a dark  green,  and  thefpec- 
trum  of  the  white  paper  became  of  a pink.  The  fpectra  then 
both  difappeared;  and  then  the  internal  fpe&rum  was  blue; 
and  then,  aiter  a fecond  difappearance,  became  yellow;  and, 
lallly,  pink;  whillt  the  fpedtrum  of  the  field  varied  into  red 
and  green. 

Thefe  lucceffions  of  different  coloured  fpectra  were  not  ex- 
actly the  fame  in  the  different  experiments,  though  obferved, 
as  near  as  could  be,  with  the  fame  quantity  of  light,  and  other 
fimilar  circumftances ; owing,  I fuppole,  to  trying  too  many 
experiments ~at  a time;  fo  that  the  eye  was  not  quite  free  from 
the  fpectra  of  the  colours  which  were  previouflv  attended  to. 

The  alternate  exertions  of  the  retina  in  the  preceding  lection, 
refembled  die  ofcitation  or  pandiculation  of  the  mufeies,  as  they 
were  performed  in  di redtions  contrary  to  each  other,  and  were 
the  confequence  of  fatigue  rather  than  of  pain.  And  in  this 
they  differ  from  the  fucceffive  diffimilar  exertions  of  the  retina, 
mentioned  in  this  fedtion,  which  refemble,  in  miniature,  the 
molt  violent  agitations  of  die  limbs  in  convullive  dileafes,  as 
cpilepfy,  chorea  S.  Viti.  and  opiflhotonos ; all  which  dileafes 

are* 


Jject.XL.  8, 9-  OCULAR  SPECTRA.  407 

are,  perhaps,  at  firft,  the  confequence  of  pain,  and  have  their 
periods  afterwards  eftabliflhed  by  habit. 

VIII.  The  retina , after  having  been  excited  into  attion  hy  a 
fiimulus  fomewhat  greater  than  the  laf  mentioned , falls 

into  a fixed fpafmodic  action, which  continues  for  fome  days.. 

1.  After  having  looked  long  at  the  meridian  fun,  in.  mak- 
ing fome  of  the  preceding  experiments,  till  the  dilk  faded  into 
a pale  blue,  I frequently  obferved  a bright  blue  fpedtrum  of  the 
fun  on  other  objedts  all  the  next  and  the  fucceeding  day,  which 
eonftantly  occurred  when  I attended  to  it,  and  frequently  when 
I did  not  previoufly  attend  to  it.  When  I clofed  and  covered 
my  eyes,  this  appeared  of  a dull  yellow ; and  at  other  times 
mixed  with  the  colours  of  other  objedts  on  which  it  was 
thrown.  It  may  be  imagined,  that  this  part  of  the  retina  was 
become  infenfible  to  white  light,  and  thence  a bluifh  fpedtruin 
became  vifible  on  all  luminous  objects;  but  as  a vellowifh 
fpedlrum  was  alfofeen  in  the  clofed  and  covered  eye,  there  can 
remain  no  doubt  of  this  being  the  fpedtrurn  of  the  fun.  A 
fimilar  appearance  was  obferved  by  M.  jEpinus,  which,  he  ac- 
knowledges, he  could  give  no  account  of.  Nov.  Com.  Petrop. 
vol.  x.  p.  2 and  6. 

The  locked-jaw,  and  fome  cataleptic  fpafms,  are  refembled 
by  this  phenomenon , and  from  hence  we  may  learn  the  danger 
to  the  eye  by  infpedting  very  luminous  objects  too  long  a time„ 

IX.  A quantity  of  Jiimulus  greater  than  the  preceding , in- 
duces a temporary  paralyfis  of  the  organ  of  vifi on. 

1.  Place  a circular  piece  of  bright  red  filk,  about  half  an 
inch  in  diameter,  on  the  middle  of  a Iheet  of  white  paper ; lay 
them  on  the  floor  in  a bright  funfhi-ne,  and  fixing  your  eyes 
fteadily  on  the  centre  of  the  red  circle,  for  three  or  four  minutes, 
at  the  diftance  of  four  or  fix  feet  from  the  object,  the  red  filk 
will  gradually  become  paler,  and  finally  ceafe  to  appear  red  at  all. 

2.  Similar  to  thefe  are  many  other  animal  fadts  ; as  purges,, 
opiates,  and  even  poifons,  and  contagious  matter,  ceafe  to  fti- 
mulafe  our  fyftem,  after  we  have  been  habituated  to  their  ufe. 
So  fome  people  fleep  undifturbed  by  a clock,  or  even  by  a forge 
hammer  in  their  neighbourhood : and  not  only  continued  irri- 
tations, but  violent  exertions  of  any  kind,  are  fueceeded  by 
temporary  paralyfis.  The  arm  drops  down  after  violent  adlion, 
and  continues  for  a time  ufelefs ; and  it  is  probable,  that  thofe 
who  have  perifhed  fuddenly  in  fwimming,  or  in  fcating  on  the 
ice,  have  owed  their  deaths  to  the  paralyfis,  or  extreme  fatigue, 
which  fucceeds  every  violent  and  continued  exertion. 

X.  Miscel- 


408 


OCULAR  SPECTRA; 


Sect.  XL.  icr. 


X.  Miscellaneous  Remarks. 

There  were  fome  circumftances  occurred  in  making  thefe 
experiments,  which  were  liable  to  alter  the  refults  of  them, 
and  which  I ihall  here  mention  for  the  affiftance  of  others,  who 
may  wiili  to  repeat  them. 

I.  Of  dir  eft  and  invcrfe  fpedlra  exifing  at  the  fame  time ; 

of  reciprocal  diredt  fpedtra ; of  a combination  of  diredt 

and  inverfe  fpedtra  ; of  a fpedlral  halo ; rules  to  predeter- 
mine the  colours  of  fpedtra. 

a.  When  an  area,  about  fix  inches  fquare,  of  bright  pink 
Indian  paper,  had  been  viewed  on  an  area,  about  a foot  fquare, 
of  white  writing  paper,  the  internal  fpedtrum  in  the  clofed  eye 
was  green,  being  the  reverfe  fpedtrum  of  the  pink  paper;  and 
the  external  fpedtrum  was  pink,  being  the  diredt  fpedtrum  of 
the  pink  paper.  The  fame  circumitance  happened  when  the 
internal  area  was  white,  and  external  one  pink  ; that  is,  the 
internal  fpedtium  was  pink,  and  the  external  one  green.  All 
the  fame  appearances  occurred  when  the  pink  paper  was  laid 
on  a black  hat. 

b.  When  fix  inches  fquare  of  deep  violet  polifhed  paper  was 
viewed  on  a foot  fquare  of  white  writing  paper,  the  internal 
fpedtrum  was  yellow,  being  the  reverfe  fpedtrum  of  the  violet 
paper,  and  the  external  one  was  violet,  being  the  diredt  fpec- 
trum  of  the  violet  paper. 

c.  When  fix  inches  fquare  of  pink  paper  was  viewed  on  a 
foot  fquare  of  blue  paper,  the  internal  lpedtrum  was  blue,  and 
the  external  fpedtrum  was  pink  ; that  is,  the  internal  one  was 
the  diredt  fpedtrum  of  the  external  objedt,  and  the  external  one 
was  the  diredt  fpedtrum  of  the  internal  objedt,  inftead  of  their 
being  each  the  reverfe  fpedtrum  of  the  objedts  they  belonged  to. 

d.  When  fix  inches  fquare  of  blue  paper  were  viewed  on  a 
foot  fquare  of  yellow  paper,  the  interior  fpedtrum  became  a 
brilliant  yellow,  and  the  exterior  one  a brilliant  blue.  The 
vivacity  of  the  fpedtra  was  owing  to  their  being  excited  both 
by  the  ftimulus  of  the  interior  and  exterior  objedts ; fo  that 
the  interior  yellow  fpedtrum  was  both  the  reverfe  fpedtrum 
of  the  blue  paper,  and  the  diredt  one  of  the  yellow  paper ; and 
the  exterior  blue  fpedtrum  was  both  the  reverfe  fpedtrum  of  the 
yellow  paper,  and  the  diredt  one  ot  the  blue  paper. 

e.  When  the  internal  area  was  only  a fquare  half-inch  of 
red  paper,  laid  on  a fquare  foot  of  dark  violet  paper,  the  inter- 
nal fpedtrum  was  green,  with  a reddifh-blue  halo.  \V  hen  the 
red  internal  paper  was  two  inches  fquare,  the  internal  fpec- 
trum  was  a deeper  green,  and  the  external  one  redder.  When 


^ct.XL.io.  OCULAR  SPECTRA.  ^409 

the  internal  paper  was  fix  inches  fquare,  the  fpe6^nm  of  it  be- 
came blue,  and  the  fpedtrum  of  the  external  paper  was  red. 

f.  When  a fquare  half-inch  of  blue  paper  was  laid  on  a fix- 
inch  fquare  of  yellow  paper,  the  fpedtrum  of  the  central  pa- 
per in  the  clofed  eye  was  yellow,  encircled  with  a blue  halo. 
On  looking  long  on  the  meridian  fun,  the  difk  fades  into  a pale 
blue,  furrounded  with  a whitifh  halo. 

Thefe  circumftances,  though  they  very  much  perplexed  the 
experiments  till  they  were  inveftigated,  admit  of  a fadsfadtory 
explanation ; for  while  the  rays  from  the  bright  internal  objedf: 
in  exp.  a.  fall  with  their  full  force  on  the  center  of  the  retina, 
and,  bv  fatiguing  that  part  of  it,  induce  the  reverfe  fpedfrum, 
many  fcattered  rays,  from  the  fame  internal  pink  paper,  fall 
on  the  more  external  parts  of  the  retina,  but  not  in  fuch  quan- 
tity as  to  occafion  much  fatigue,  and  hence  induce  the  diredt: 
fpedtrum  of  the  pink  colour  in  thole  parts  of  the  eye.  The 
fame  reverfe  and  diredt  fpedtra  occur  from  the  violet  paper  in 
exp.  b. : and  in  exp.  c.  the  fcattered  rays  from  the  central  pink 
paper,  produce  a diredt  fpedtrum  of  this  colour  on  the  external 
parts  of  the  eye  ; while  the  fcattered  rays  from  the  external  blue 
paper  produce  a diredt  fpedfrum  of  that  colour  on  the  central 
part  of  the  eye,  inftead  of  thefe  parts  of  the  retina  falling  reci- 
procally into  their  reverfe  fpedfra.  In  exp.  cl.  the  colours  be- 
ing the  reverfe  of  each  other,  the  fcattered  rays  from  the  exte- 
rior objedf  falling  on  the  central  parts  of  the  eye,  and  there  ex- 
citing their  diredf  fpedfrum,  at  the  fame  time  that  the  retina  was 
excited  into  a reverfe  fpedfrum  by  the  central  objedf,  and  this 
diredt  and  reverfe  fpedfrum  being  of  fimilar  colour,  the  fupe- 
rior  brilliancy  of  this  fpedfrum  was  produced.  In  exp.  e.  the 
effect  of  various  quantities  of  ftimulus  on  the  retina,  from  the 
different  refpedtive  fixes  of  the  internal  and  external  areas,  in- 
duced a fpedtrum  of  the  internal  area  in  the  center  of  the  eye, 
combined  of  the  reverfe  fpedfrum  of  that  internal  area,  and  the 
diredf  one  of  the  external  area,  in  various  fhades  of  colour, 
from  a pale  green  to  a deep  blue,  with  fimilar  changes  in  the 
fpedfrum  of  the  external  area.  For  the  fame  reafons,  when 
an  internal  bright  objedf  was  fmall,  as  in  exp.  f.  inftead  of  the 
whole  of  the  fpedfrum  of  the  external  objedf  being  reverfe  to 
die  colour  of  the  internal  objedf,  only  a kind  of  halo,  or  radia- 
tion of  colour,  fimilar  to  that  of  the  internal  objedf,  was  fpreacl 
a little  way  on  the  external  fpedfrum.  For  this  internal  blue 
area  being  fo  fmall,  the  fcattered  rays  from  it  extended  but  a 
little  way  on  the  image  of  the  external  area  of  yellow  paper, 
and  could  therefore  produce  only  a blue  halo  round  the  yellow 
fpedtrum  in  the  center. 


Hhh 


If 


4io 


OCULAR  SPECTRA. 


Sect.  XL.  r o. 


If  any  one  fhould  fufpect  that  the  fcattered  rays  from  the 
exterior  colored  object,  do  not  intermix  with  the  rays  from 
the  interior  coloured  object,  and  thus  affedt  the  central  part 
of  the  eye,  let  him  look  through  an  opake  tube,  about  two 
feet  in  length,  and  an  inch  in  diameter,  at  a coloured  wall  of 
a room  with  one  eye,  and  with  the  other  eye  naked  ; and  he 
will  find,  that  by  /hutting  out  the  lateral  light,  the  area  of  the 
wail  feen  through  a tube,  appears  as  if  illuminated  by  the  fun- 
fhine,  compared  with  the  other  parts  of  it ; from  whence  arifes  the 
advantage  of  looking  through  a dark  tube  at  diftant  paintings. 

Hence  we  may  lately  deduce  the  following  rules  to  determine 
before -hand  the  colours  of  all  ipeclra.  i.  The  direct  fpedtrum 
without  any  lateral  light  is  an  evanefcent  reprefentation  of  its 
objedt  in  the  unfatigued  eye.  2.  With  fome  lateral  light  it 
becomes  of  a colour  combined  or  the  direct  fpedtrum  of  the 
central  objedt,  and  of  the  circumjacent  objedts,  in  proportion 
to  their  refpeditive  quantity  and  brilliancy.  3.  The  reverfe 
fpedtrum,  without  lateral  light,  is  a reprefentation,  in  the  fatigued 
eye,  of  the  form  of  its  objects,  with  luch  a colour  as  would  be 
produced  by  all  the  primary  colours,  except  that  of  the  objedt. 
4.  With  lateral  light  the  colour  is  compounded  of  the  reverfe 
• fpedtrum  of  the  central  objedt,  and  the  diredt  lpedtrum  of  the 
circumjacent  objedts,  in  proportion  to  their  refpective  quantity 
and  brilliancy. 

2.  Variation  and  vivacity  of  the  fpeftra  occajioned  ly  ex- 
traneous light. 

The  reverfe  fpedtrum,  as  has  been  before  explained,  is  fimi- 
lar  to  a colour,  formed  by  a combination  of  all  the  primary 
colours,  except  that  with  which  the  eye  has  been  fatigued  in 
making  the  experiment ; fo  the  reverfe  fpedtrum  of  red  is  fucli 
a green  as  would  be  produced  by  a combination  of  all  the  other 
prifmatic  colours.  Now,  it  muft  be  obferved,  that  this  reverfe 
fpedtrum  of  red  is  therefore  the  diredt  fpedtrum  of  a combina- 
tion of  all  the  other  prifmatic  colours,  except  the  red;  whence, 
on  removing  the  eve  from  a piecctof  red  filk  to  a fheet  of  w hite 
paper,  the  green  fpedtrum,  which  is  perceived,  may  either  be 
called  the  reverfe  fpedtrum  cf  the  red  111k,  or  the  diredt  lpec- 
trum  of  all  the  rays  from  the  white  paper,  except  the  red;  for 
in  truth  it  is  both.  Hence  we  fee  the  reaion  why  it  is  not  eafy 
to  gain  a diredt  fpedtrum  of  any  coloured  objedt  in  the  day-time, 
where  there  is  much  lateral  light,  except  of  very  bright  objedts, 
as  ©f  the  fetting  fun,  or  by  looking  through  an  opake  tube; 
bee  a ufe  the  lateral  external  light  tailing  alfo  on  the  centra:  part 
of  the  retina,  contributes  to  induce  the  reverfe  fpedtrum,  w hich 


Sect.  XL.  io.  OCULAR  SPECTRA. 


41a 

is  at  the  fame  time  the  direct  fpeftrum  of  that  lateral  light,  de- 
ducing only  the  colour  of  the  central  objeC  which  we  have 
been  viewing.  And,  for  the  fame  reafon,  it  is  difficult  to  gain 
the  reverfe  fpeCrum,  where  there  is  no  lateral  light  to  contribute 
to  its  formation.  Thus,  in  looking  through  an  opake  tube  on 
a yellow  wall,  and  doling  my  eye,  without  admitting  any  lateral 
light,  the  fpeCra  were  all  at  fir  ft  yellow,  but  at  length  changed 
into  blue.  And  on  looking,  in  tire  fame  manner,  on  red  paper, 
I did  at  length  get  a green  fpeCrntn ; hut  they  were  all  at  firft 
red  ones : and  the  fame  after  looking  at  a candle  in  the  night. 

The  reverfe  fpeCrum  was  formed,  with  greater  facility,  when 
the  eye  was  thrown  from  the  objeC  on  a fheet  of  white  paper, 
or  when  light  was  admitted  through  the  clofed  eye-lids ; becaufe 
not  only  the  fatigued  part  of  the  retina  was  inclined  fponta- 
neoufly  to  fall  into  motions  of  a contrary  diredtion  ; but  being 
'ftill  fenfible  to  all  other  rays  of  light  except  that  with  which  it 
was  lately  fatigued,  was,  by  tlrefe  rays,  ftimulated  at  the  fame 
time  into  thofe  motions  which  form  the  reverfe  fpeCrum. — 
H ence,  wrhen  the  reverfe  fpeCrum  of  any  colour  became  faint, 
it  was  wonderfully  revived  by  admitting  more  light  through  the 
eye-lids,  by  removing  the  hand  from  before  them : and  hence, 
on  covering  the  clofed  eye -lids,  the  fpectrum  would  often  ceafe 
for  a time,  till  the  retina  became  fenfible  to  the  ftimulus  of  the 
fmaller  quantity  of  light,  and  then  it  recurred.  Nor  was  the 
fpedtrum  only  changed  in  vivacity,  or  in  degree,  by  this  admif- 
fion  of  light  through  the  eye-lids.;  but  it  frequently  happened, 
after  having  viewed  bright  objects,  that  the  fpeCrum  in  the  clofed 
and  covered  eye  was  changed  into  a third  fpeCrum,  when  light 
was  admitted  through  the  eye-lids ; which  third  fpedtrum  was 
compofed  of  fuch  colours  as  could  pafs  through  the  eye-lids, 
except  thofe  of  the  cbjedt.  Thus,  when  an  area  of  half  an 
inch  diameter  of  pink  paper  was  viewed  on  a fheet  of  white 
paper  in  the  funfhine,  the  fpectrum  with  clofed  and  covered 
eyes  was  green;  but  on  removing  the  hands  from  before  the 
clofed  eye-lids,  the  fpedtrum  became  yellow,  and  returned  in- 
ftantly  again  to  green,  as  often  as  the  hands  were  applied  to 
cover  the  eye-lids,  or  removed  from  them : for  the  retina  being 
now  infenfible  to  red  light,  the  yellow  rays  palling  through  the 
eye-lids  in  greater  quantity  than  the  other  colours,  induced  a 
yellow  fpedtrum ; whereas,  if  the  fpedtrum  was  thrown  on 
white  paper,  with  the  eyes  open,  it  became  only  a lighter  green. 

Though  a certain  quantity  of  light  facilitates  the  formation 
of  the  reverfe  fpedlrum,  a greater  quantity  prevents  its  forma- 
tion, as  the  more  powerful  ftimulus  excites  even  the  fatigued 
parts  of  the  eye  into  adtion ; otherwife  we  fhould  fee  the  fpeo 

tnjm 


412 


OCULAR  SPECTRA. 


Sect.  XL.  io. 


trum  of  the  laft  viewed  object  as  often  as  we  turn  our  evej, 
Hence  the  reverfe  fpeccra  are  heft  feen  by  gradually  approach- 
ing lire  hand  near  the  clofed  eye-lids  to  a certain  diftance  only, 
which  mu  ft  be  varied  with  the  brightnefs  of  the  day,  or  the 
energy  of  the  fpedrum.  Add  to  this,  that  all  dark  fpedra,  as 
black,  blue,  or  green,  it  light  be  admitted  through  the  eye-lids, 
alter  they  have  been  fome  time  covered,  give  reddifh  fpedra, 
for  the  reafons  given  in  Sed.  III.  Exp.  i. 

From  thefe  circumftances  of  the  extraneous  light  coinciding 
with  the  fpontaneous  efforts  of  the  fatigued  retina  to  produce 
a reverfe  ipedrum,  as  was  obferved  before,  it  is  not  eafy  to 
gain  adiredt  fpedrum,  except  of  objeds  brighter  than  the  am- 
bient light;  fuch  as  a candle  in  the  night,  the  fetting  fun,  or 
viewing  a bright  objed  through  an  opake  tube;  and  then  the 
reverfe  fpedrum  is  inftantanebufly  produced  by  the  admiffion 
ol‘  fome  external  light,  and  is  as  inftantly  converted  again  to 
the  dired  fpedrum  by  the  exclusion  of  it.  Thus,  on  looking 
at  the  fetting  fun,  on  doling  the  eyes,  and  covering  them,  a 
yellow  fpedrum  is  feen,  which  is  the  dired  fpedrum  of  the 
fetting  fun ; but  on  opening  the  eyes  on  the  fky,  the  yellow 
fpedrum  is  immediately  changed  into  a blue  one,  which  is  the 
reverfe  fpedrum  of  the  yellow  fun,  or  the  dired  fpedrum  of 
the  blue  fky,  or  a combination  of  both.  And  this  is  again 
transformed  into  a yellow  one  on  doling  the  eves,  and  fo  reci- 
procally, as  quick  as  the  motions  of  the  opening  and  doling 
eye-lids.  Hence,  when  Mr.  Melvill  obferved' the  fcintillations 
of  the  ftar  Sirius  to  be  fometimes  coloured,  thefe  were  proba- 
bly the  aired  fpedrum  of  the  blue  fky  on  the  parts  of  the  re- 
tina fatigued  by  the  white  light  of  the  ftar.  Effays  Pbyfical 
and  Literary,  p.  81.  vol.  ii. 

When  a aired  fpedrum  is  thrown  on  colours  darker  than 
itfelf,  it  mixes  with  them;  as  the  yellow  Ipedrum  of  the  letting 
fun,  thrown  on  the  green  grafs,  becomes  a greener  yellow. 
But  when  a aired  fpedrum  is  thrown  on  colours  brighter  than 
itfelf,  it  becomes  inftantly  changed  into  the  revere  Ipedrum, 
which  mixes  with  thofe  brighter  colours.  So  the  yellow  fpec- 
trum  of  the  fetting  lun,  thrown  on  the  luminous  ft  v.  becomes 
blue,  and  chancres  with  the  colour  or  brighmels  of  the  clouds  ou 
which  it  appears.  But  the  reverfe  fpedrum  mixes  with  every 
kind  of  colour  on  which  it  is  thrown,  whether  brighter  than  it- 
felf or  not:  thus  the  reverfe  fpedrum,  obtained  by  viewing  a 
piece  of  yellow  ft lk,  when  thrown  on  white  paper,  was  a lucid 
blue  green;  when  thrown  on  black  Turkey  leather,  becomes 
a deep  violet.  And  the  fpedrum  of  blue  ftlk,  thrown  on  wji:;c 
paper,  was  a light  yellow ; on  black  ftlk  was  an  obfeure  orange 


Sect.  XL.  10. 


OCULAR  SPECTRA. 


4J3 

and  die  blue  fpedlrum,  obtained  from  orange  coloured-filk,  . 
thrown  on  yellow,  became  a green. 

In  thefe  cafes  the  retina  is  thrown  into  addivity  or  fenfariop 
by  the  ftimulus  of  external  colours,  at  the  fame  time  that  if 
continues  the  activity  or  fenfation  which  forms  the  fpedfra ; in 
the  fame  manner  as  the  prifinatic  colours,  painted  on  a whirling 
top,  are  feen  to  mix  together.  When  thefe  colours  of  extern 
jial  objects  are  brighter  than  the  direct  fpectrum  which  is  thrown 
upon  them,  they  change  it  into  the  reverfe  fpedtrum,  like  the 
admiffion  of  external  light  on  a diredt  fpedtrum,  as  explained 
above.  When  they  are  darker  than  the  diredt  fpedtrum,  they 
mix  with  it,  their  weaker  ftimulus  being  infufficiept  to  induce 
ffte  reverfe  fpedtrum. 

3.  Variation  of fipeVra  in  rcfpcff  to  number,  and  figure,  and 
remifiion. 

When  we  look  long  and  attentively  at  any  objedt,  the  eye 
.cannot  always  be  kept  entirely  motionlcfs;  hence,  on  infpedt- 
ing  a circular  area  of  red  filk  placed  on  white  paper,  a lucid 
crefcent  or  edge  is  feen  to  librate  on  one  fide  or  other  of  the 
red  circle:  for  the  exterior  parts  of  the  retina  fometimes  falling 
on  the  edge  of  the  central  iilk,  and  fometimes  on  the  white  pa- 
per, are  lefs  fatigued  with  red  light  than  the  central  part  of  the 
retina,  which  is  conftantly  expofedto  it;  and  therefore,  when 
they  fall  on  the  edge  of  the  red  filk,  they  perceive  it  more  vi- 
vidly. Afterwards,  when  the  eye  becomes  fatigued,  a green 
fpedtrum,  in  the  form  of  a crefcent,  is  feen  to  librate  on  one  fide 
or  other  of  the  central  circle  ; as  by  the  unfteadinefs  of  the  eye 
a part  of  the  fatigued  retina  fails  on  the  white  paper;  and  as,  by 
the  increafing  fatigue  of  the  eye,  the  central  part  of  the  filk  ap- 
pears paler,  the  edge  on  which  the  unfatigued  part  of  the  retina 
occafionally  falls  will  appear  of  a deeper  red  than  the  original 
filk,  becaufe  it  is  compared  with  the  pale  internal  part  of  it. 
M.  de  BufFon,  in  making  this  experiment,  obferved,  that  the 
red  edge  of  the  filk  was  not  only  deeper  coloured  than  the  ori- 
ginal filk ; but,  on  his  retreating  a little  from  it,  it  became  oblong, 
and  at  length  divided  into  two,  which  muft  have  been  owing 
to  his  obferving  it  either  before  or  behind  the  point  of  interfec- 
tion  of  the  two  optic  axifes.  Thus,  if  a pen  is  held  up  before 
a diftant  candle,  whep  we  look  intenfely  at  the  pen,  two  can- 
dies are  feen  behind  it;  when  we  look  intenlely  at  the  candle, 
two  pens  are  feen.  If  the  fight  be  unfteady  at  the  time  of  be- 
1 mlding  the  fpn,  even  though  one  eye  only  be  ufed,  many  image? 
ot  the  inn  will  appear,  or  luminous  lines,  when  the  eye  isclofed. 
And  as  fome  parts  of  thefe  will  be  more  vivid  than  others,  and 

fome 


414 


OCULAR  SPECTRA.  Sect.  XL.  ic. 


fome  parts  of  them  will  be  produced  nearer  the  center  of  the  eye 
than  others,  thefe  will  difappear  fooner  than  the  others  ; and 
hence  the  number  and  fhape  of  thefe  fpedtra  of  the  fun  will 
continually  vary,  as  long  as  they  exift.  The  caufe  of  fome 
being  more  vivid  than  others,  is  the  unfteadinefs  of  the  eye  of 
the  beholder,  fo  that  fome  parts  of  the  retina  have  been  longer 
expofed  to  the  fun-beams.  That  fome  parts  of  a complicated 
fpedtrum  fade  and  return  before  other  parts  of  it,  the  following 
experiment  evinces.  Draw  three  concentric  circles ; the  ex- 
ternal one  an  inch  and  a half  in  diameter,  the  middle  one  an 
inch,  and  the  internal  one  half  an  inch ; colour  the  external 
and  internal  areas  blue,  and  the  remaining  one  yellow,  as  in 
Fig.  5. ; after  having  looked  about  a minute  on  the  center  of 
thefe  circles,  in  a bright  light,  tire  fpecfrum  of  the  external 
area  appears  firft  in  the  doled  eye,  then  the  middle  area,  and 
laftly  the  central  one;  and  then  the  central  one  difappears,  and 
the  others  in  inverted  order.  If  concentric  circles  of  more  co- 
lours are  added,  it  produces  the  beautiful  ever  changing  fpec- 
trum  in  Se£I.  L Exp.  2. 

From  hence  it  would  feem,  that  the  center  of  the  eye  pro- 
duces quicker  remiffions  of  fpedra,  owing,  perhaps,  to  its 
greater  fenfibility  ; that  is,  to  its  more  energetic  exertions. 
Thefe  remiffions  of  fpeccra  bear  fome  analogy  to  the  tremors 
of  the  hands,  and  palpitations  of  the  heart,  of  weak  people ; 
and  perhaps  a criterion  of  the  ftrength  of  any  mufcle  or  nerve 
may  be  taken  from  the  time  it  can  be  continued  in  exertion. 

4.  Variation  of  fpeffra  in  rcfpebl  to  brilliancy : the  vijlbility 
of  the  circulation  of  the  blood  in  the  eye. 

1.  The  meridian  or  evening  light  makes  a difference  in  the 
colours  of  fome  fpedra  ; for  as  the  fun  defeends,  the  red  rays, 
which  are  lefs  refrangible  by  the  convex  atmofphere,  abound 
in  great  quantity.  Whence  the  lpecirum  of  the  light  pails  of 
a window  at  this  time,  or  early  in  the  morning,  is  red ; and 
becomes  blue,  either  a little  later  or  earlier;  and  white  in  the 
meridian  day ; and  is  alfo  variable,  from  the  colour  of  the 
clouds  or  fky  which  are  oppoled  to  the  window. 

2.  All  thefe  experiments  are  liable  to  be  confounded,  if  they 
are  made  too  loon  after  each  other,  as  the  remaining  fpeefrum 
will  mix  with  the  new  ones.  This  is  a very  troublefome  cir- 
cumftance  to  painters,  who  are  obliged  to  look  long  upon  the 
fame  colour ; and  in  particular  to  thofe  whofe  eyes,  from  na- 
tural debility,  cannot  long  continue  the  fame  kind  of  exertion. 
For  the  fame  reafon,  in  making  thefe  experiments,  the  reiult 
becomes  much  varied  if  the  eyes,  after  viewing  any  objecEl,  are 

removed 


w . ■■ 

. 

’■ 

. ■ * 

' 

. .v-  - • . "3v\M s&  ig&Vm 

■ 

- 

■ ■ ■: 


<pg  • 

: V'  ■■  • 

! V ‘ 

* 

: • 

••••  .■  ' • 


Sect.  XL.  io*  , OCULAR  SPECTRA; 


4i5 

removed  on  other  objedts  for  but  an  inftant  of  time,  before  we 
clofe  them  to  view  the  fpedlrum;  for  the  light  from  the  objedt, 
of  which  we  had  only  a tranfient  view,  in  the  very  time  of 
clofing  our  eyes,  adts  as  a ftimulus  on  the  fatigued  retina,  and 
for  a time  prevents  the  delired  fpedtrum  from  appearing,  or 
mixes  its.  own  fpedtrum  with  it.  Whence,  after  the  eye-lids 
are  clofed,  either  a dark  field,  or  fome  unexpected  colours,  are 
beheld  for  a few  feconds,  before  the  defired  fpedtrum  becomes 
diftindtly  vifible. 

3.  The  length  of  time  taken  up  in  viewing  an  objedt,  of 
which  we  are  to  obferve  the  fpedtrum,  makes  a great  difference 
in  the  appearance  of  the  fpedtrum,  not  only  in  its  vivacity,  but 
in  its  colour  ; as  the  diredt  fpedtrum  of  the  central  object,  or 
of  the  circumjacent  ones,  and  alfo  the  reverfe  fpedtra  of  both, 
with  their  various  combinations,  as  well  as  the  time  of  their 
duration  in  the  eye,  and  of  their  remiffions  or  alterations,  de- 
pend upon  the  degree  of  fatigue  the  retina  is  fubjedted  to.  The 
Chevalier  d’Arcy  conftrudted  a machine,  by  which  a coal  of 
fire  was  whirled  round  in  the  dark,  and  found,  that  when  a lu- 
minous body  made  a revolution  in  eight  thirds  of  time,  it  pre- 
fented  to  the  eye  a complete  circle  of  fire ; from  whence  he 
concludes,  that  the  impreffion  continues  on  the  organ  about  the 
feventh  part  of  a fecond.  Alem. del’ Acad.  desSc.  1765.  This, 
however,  is  only  to  be  confidered  as  the  fhorteft  time  of  the 
duration  of  thefe  diredt  fpedtra ; fince,  in  the  fatigued  eye,  both 
the  diredt  and  reverfe  fpedtra,  with  their  intermiffions,  appear  - 
to  take  up  many  feconds  of  time,  and  feem  very  variable,  in 
proportion  to  the  circumftances  of  fatigue  or  energy. 

4.  It  fometimes  happens,  if  the  eye-balls  have  been  rubbed 
hard  with  the  fingers,  that  lucid  fparks  are  feen,  in  quick  mo- 
tion, amidft  the  fpedtrum  we  are  attending  to.  This  is  fimilar 
to  the  flafbes  of  fire  from  a ltroke  on  the  eye  in  fighting,  and 
is  refembled  by  the  warmth  and  glow  which  appears  upon  the 
fkin  after  fridtion,  and  is  probably  owing  to  an  acceleration  of 
the  arterial  blood  into  the  veffels  emptied  by  the  previous  pref- 
fure.  By  being  accuftomed  to  obferve  fuch  final!  fenfations  in 
the  eye,  it  is  eafy  to  fee  the  circulation  of  the  blood  in  this  or- 
gan. I have  attended  to  this  frequently,  when  1 have  obferved 
my  eyes  more  than  commonly  fenfible  to  other  fpedfra.  The 
circulation  may  be  feen  either  in  both  eyes  at  a time,  or  only  in 
one  of  them ; for,  as  a certain  quantity  of  light  is  neceffary  to 
produce  this  curious  phenomenon,  if  one  hand  be  brought 
nearer  the  clofed  eye-lids  than  the  other,  the  circulation  in  that 
eye  will  for  a time  difappear.  For  the  eafier  viewing  the  cir- 
culation, it  is  fometimes  neceffary  to  rub  the  eyes  with  a certain 

I i i degree 


OCULAR  SPECTR  A.  Se ct.  XL.  to- 


416 

degree  of  force,  after  they  are  clofed,  and  to  hold  the  breath  ra- 
ther longer  than  is  agreeable,  which,  by  accumulating  more 
blood  in  the  eye,  facilitates  the  experiment ; but,  in  general,  it 
may  be  feen  diftinftly  after  having  examined  other  fpedfra  with 
your  back  to  the  light,  till  the  eyes  become  w’eary ; then  hav- 
ing covered  your  clofed  eye-lids  for  half  a minute,  till  the  fpec- 
trum  is  faded  away  which  you  were  examining,  turn  your  tace 
to  the  light,  and  removing  your  hands  from  the  eye-lids,  bv  and 
by  again  (hade  them  a little,  and  the  circulation  becomes  cu- 
rioufly  didindt.  The  dreams  of  blood  are,  how'ever,  generally 
feen  to  unite,  which  fhews  it  to  be  the  venous  circulation,  ow- 
ing, I fuppofe,  to  the  greater  opacity  of  the  colour  of  the  blood 
in  thefe  veflels ; for  this  venous  circulation  is  alfo  much  more 
eafily  feen  by  the  microfcope  in  the  tail  of  a tadpole. 

5/  Variation  of  [peffra  in  rcfpeft  to  diflinffnefs  and  fize  ; 
with  a new  way  of  magnifying  objcdls. 

1.  It  was  before  obferved,  that  when  the  two  colours  viewed 
together  were  oppofite  to  each  other,  as  yellow  and  blue,  red 
and  green,  &c.  according  to  the  table  of  reflections  and  tranf- 
miflions  of  light  in  Sir  Ifaac  Newton’s  Optics,  B.  II.  fig.  3.  the 
fpedfra  of  thofe  colours  were  of  all  others  the  mod  brilliant, 
and  bed  defined ; becaufe  they  were  combined  of  the  reverfe 
fpedfrum  of  one  colour,  and  of  the  diredt  fpedfrum  of  the  other. 
Hence,  in  books  printed  with  fmall  tvpes,  or  in  the  minute  gra- 
duation of  thermometers,  or  of  clock-faces,  which  are  to  be 
feen  at  a dfdanee,  if  the  letters  or  figures  are  coloured  with 
orange,  and  the  ground  with  indigo ; or  the  letters  with  red, 
and  the  ground  with  green;  or  any  other  lucid  colour  is  ufed 
for  the  letters,  the  lpedfrum  of  which  is  fimilar  to  the  colour 
of  the  ground;  fuch  letters  will  be  feen  much  more  didindflv, 
and  with  lefs  conlufion,  than  in  black  or  white : for,  as  the  fpec- 
trum  of  the  letter  is  the  fame  colour  with  the  ground  on  which 
they  are  feen,  the  undeadinefs  of  the  eye  in  long  attending  to 
them,  will  not  produce  coloured  lines  by  the  edges  of  the  letters, 
which  is  the  principal  caufe  of  their  confufion.  The  beauty 
of  colouis  lying  in  vicinity  to  each  other,  whole  fpedfra  are 
thus  reciprocally  fimilar  to  each  colour,  is  owing  to  this  greater 
eale  that  the  eye  experiences  in  beholding  them  didindflv ; and 
it  is  probable,  in  die  orgairof  hearing,  a fimilar  circumllance 
may  conditute  the  pieaiure  or  melody.  Sir  Ifaac  Newton  ob- 
ferves,  that  gold  and  indigo  were  agreeable  when  viewed  toge- 
ther ; and  thinks  there  may  be  fome  analogy  between  the  ienla- 
iions  of  light  and  found.  Optics,  Qu.  14. 

In  viewing  the  fpedtra  ©f  bright  objedts,  as  of  an  area  of 

red 


- 


- ■*  i i!  }l'  ’ y\4  :f  K 

. 


- 


■ 


' J • «!' 


, 


i” 

I ■ 

I ' i 


* 

* 


% 


OCULAR  SPECTRA. 


Sect.  XL.  io. 


4*7 


yed  filk  of  half  an  inch  diameter  on  white  paper,  it  is  eafy  tq 
magnify  it  to  tenfold  its  fize : for  if,  when  the  fpedhum  is  form- 
ed, you  ftill  keep  your  eye  fixed  on  the  filk  area,  and  remove 
it  a few  inches  further  from  you,  a green  circle  is  feen  round 
the  red  filk : for  the  angle  now  fubtended  by  the  filk  is  lefs  than 
}t  was  when  the  fpedtrum  was  formed,  but  that  of  the  fpec- 
Jtrum  continues  the  fame,  and  our  imagination  places  them  at 
Xhe  fame  diftance.  Thus,  when  you  view  a fpedlrum  on  a 
fheet  of  white  paper,  if  you  approach  the  paper  to  the  eye,  yoq 
may  diminifh  it  to  a point ; and  if  the  paper  is  made  to  recede 
from  the  eye,  the  fpedtrum  will  appear  magnified  in  proportion 
to  the  diftance. 

I was  furprifed,  and  agreeably  amufed,  with  the  following 
experiment.  I covered  a paper  about  four  inches  fquare,  with 
yellow,  and  with  a pen,  filled  with  a blue  colour,  wrote  upon 
the  middle  of  it,  the  word  BANKS,  in  capitals,  as  in  Fig.  6. 
and  fitting  with  my  back  to  the  fun,  fixed  my  eyes  for  a mi- 
nute exadtly  on  the  center  of  the  letter  N in  the  middle  of  the 
word  ; after  clofing  my  eyes,  and  {hading  them  fomewhat  with 
my  hand,  the  word  was  diftindtly  feen  in  the  fpedtrum  in  yel- 
low letters  on  a blue  field ; and  then,  on  opening  my  eyes  on  a 
yellowifti  wall  at  twenty  feet  diftance,  the  magnified  name  of 
BANKS  appeared  written  op  the  wall  in  golden  characters. 


Conclufion. 


It  was  obferved  by  the  learned  M.  Sauvages,  (Nofol.  Me- 
thod. Cl.  VIII.  Ord.  1.)  that  the  pulfations  of  the  optic  artery 
tnight  be  perceived  by  looking  attentively  on  a white  wall  well 
illuminated.  A kind  of  net-work,  darker  than  the  other  parts 
of  the  wall,  appears  and  vanifhes  alternately  with  every  pulfa- 
tion.  This  change  of  the  colour  of  the  wall  he  well  afcribes 
to  the  compreflion  of  the  retina,  by  the  diaftole  of  the  artery. 
The  various  colours  produced  in  the  eye  by  the  preflure  of  the 
finger,  or  by  a ftroke  on  it,  as  mentioned  by  Sir  Ifaac  New- 
ton, feem  likewife  to  originate  from  the  unequal  preflure  on 
various  parts  of  the  retina.  Now,  as  Sir  Ifaac  Newton  has 
{hewn,  that  all  the  different  colours  are  refledted  or  tranfmit- 
ted  by  the  laminae  of  foap  bubbles,  or  of  air,  according  to  their 
different  thicknefs  or  thinnefs,  is  it  not  probable,  that  the  effedt 
of  th&adtivity  of  the  retina  may  be  to  alter  its  thicknefs  or  thin- 
nefs, fo  as  better  to  adapt  it  to  refledt  or  tranfmit  the  colours 
which  ftimulate  it  into  adtion  ? May  not  mufcular  fibres  exift 
in  the  retina  for  this  purpofe,  which  may  be  lefs  minute  than 
the  locomotive  mufcles  of  microfcopic  animals  ? May  not  thefe 

mufcular 


4!8  OCULAR  SPECTRA.  Sect.XL.io. 

mufcular  actions  of  the  retina  conftitute  the  fenfation  of  light 
and  colours : and  the  voluntary  repetitions  of  them,  when  the 
objedt  is  withdrewn,  conftitute  our  memory  of  them  ? And 
laffcly,  may  not  the  laws  of  the  lenfations  of  light,  here  invef- 
tigated,  be  applicable  to  all  our  other  fenfes,  and  much  con- 
tribute to  elucidate  many  phenomena  of  animal  bodies,  both  in 
■their  healthy  and  dileafed  ftate  ; and  thus  render  this  invetliga- 
tion  well  worthy  the  attention  of  the  phyfician,  die  raetaphv- 
fician,  and  the  natural  philolpher  ? 

November  i,  1785. 

Dum,  Liber ! astra  petis  volitans  trepidantibus  alis, 

Imiis  immemori,  parvula  gutta,  mari. 

Me  quoque,  me  currente  rota  revolubiiis  a?ta$ 

Volverit  in  tenebras, — i,  Liber,  ipse  sequor. 


,*>tq  or  the  first  v o trxi. 


INDEX. 


TO  THE  - 

SECTIONS  OF  PART  FIRST, 


A 

ABSORPTION  of  solids,  xxxiii.  3.  1.  xxxvii. 

........  of  fluids  in  anasarca,  xxxv.  1.  3, 

Absorbent  vessels,  xxii.  2.  xxix.  1. 

-----  regurgitate  their  fluids,  xxix.  2,. 

- - - - - their  valves,,  xxix.  2. 

-----  communicate  with  vena  portarum,  xxvii.  20- 
Accumulation  of  sensorial  power,  iv.  2.  xii.  5.  2. 

Activity  of  system  too  great,  cure  of,  xii.  6. 

- - - - too  small,  cure  of,  xx.  7. 

Age,  old,  xii.  3,  1.  xxxvii.  4. 

Ague-fit,  xii.  7.  1.  xxxii.  3.  4.  xxxii.  9. 

how  cured  by  bark,  xii.  3.  4. 

- - - - - periods,  how  occasioned,  xii.  2.  3.  xxxii.  3.  4.  xvii.  3. 6-, 
Ague  cakes,  xxxii.  7.  xxxii.  9. 

Air,  sense  of  fresh,  xiv,  8. 

injures  ulcers,  xxviii.  2. 

injedied  into  veins,  xxxii.  5. 

Alcohol  deleterious,  xxx.  3. 

Alliterations,  why  agreeable,  xxii.  2. 

Aloes  in  lessened  doses,,  xii.  3.  1. 

American  natives  indolent,  xxxi.  2. 

- narrow  shouldered,  xxxi.  1. 

Analogy  intuitive,  xvii.  3.  7. 

Animals  less  liable  to  madness,-  xxxiii.  1. 

- - - - less  liable  to  contagion,  xxxiii.  1. 

....  how  to  teach,  xxii.  3.  2. 

-----  their  similarity  to  each  other,  xxxix.  4.  8. 

- - - - their  changes  after  nativity,  xxxix.  4.  8. 

- - - - their  changes  before  nativity,  xxxix.  4.  8. 

- - - - less  liable  to  contagious  diseases,  why,  xxxiii.  1.  3. 

- - - - less  liable  to  delirium  and  insanity,  why,  xxxiii.  1.  5. 

- - - - easier  to  preserve  than  to  reproduce,  xxxvii. 

. . . . food,  distaste  of,  xxxviii.  1. 

, r - - - appetency,  xxxix.  4.  7. 

Antipathy,  x.  2.  2. 

Appetites,  xi.  2.  2.  xiv.  8. 

Aphthae, 


420 


INDEX. 


Aphthae,  xxviii. 

Apoplexy,  xxxiv.  i.  7. 

* - - - - not  from  deficient  irritation,  xxxii.  2.  1. 

Architecture,  xii.  3.  3.  xvi.  10. 

Arts,  fine,  xxii.  2. 

Asparagus,  its  smell  in  urine,  xxix. 

Association  defined,  ii.  11.  iv.  7.  v.  2. 

------  associate  motions,  x. 

------  stronger  than  irritative  ones,  xxiv.  2.  8. 

......  formed  before  nativity,  xi.  3. 

......  with  irritative  ones,  xxiv.  8. 

......  with  retrograde  ones,  xxv.  7.  xxv.  10.  xxv.  if. 

......  diseases  from,  xxxv. 

Asthma,  xviii.  15. 

Attention,  language  of,  xvi.  8.  6. 

Atrophy,  xxviii. 

Aversion,  origin  of,  xi.  2.  3. 

B 

Balance  ourselves  by  vision,  xx.  1. 

Bandage  increases  absorption,  xxxiii.  2.  11. 

Barrenness,  xxxvi.  2.  3. 

Battement  of  sounds,  xx.  7. 

Bath,  cold.  See  Cold  Bath. 

Beauty,  sense  of,  xvi.  6.  xxii.  2. 

Bile^dufts,  xxx. 

stones,  xxx.  3. 

regurgitates  into  the  blood,  xxiv.  2.  7. 

- - - vomiting  of,  xxx.  3. 

Birds  of  passage,  xvi.  12. 

- - - nests  of,  xvi.  13. 

- - - colour  of  their  eggs,  xxxix.  5. 

Biting  in  pain,  xxxiv.  1.  3. 

- - - of  mad  animals,  xxxiv.  r.  3. 

Black  spots  on  dice  appear  red,  xl.  3. 

Bladder,  communication  of  with  the  intestines,  xxix.  3. 

- - - - of  fish,  xxiv.  1 . 4. 

Biood,  transfusion  of  in  nervous  fevers,  xxxii.  4. 

- - - deficiency  of,  xxxii.  2.  and  4. 

- - - from  the  vena  portarum  into  the  intestines,  xxvii.  2. 

- - - its  momentum,  xxxii  5.  2. 

- - - momentum  increased  by  venesection,  xxxii.  5.  4. 

- - - drawn  in  nervous  pains,  xxxii.  5.  4. 

- - - its  oxygenation,  xxxviii. 

Breathing,  how  learnt,  xv.  4. 

Breasts  of  men,  xiv.  8. 

Brutes  differ  from  men,  xi.  2.  3.  xvi.  17. 

Brutes.  See  Animals. 

Buxton  bath,  why  it  feels  warm,  xii.  2.  r.  xxxii.  3.  3. 

Capillary 


INDEX. 


4aj 


C 

Capillary  vessels  are  glands,  xxvi.  x. 

Catalepsy,  xxxiv.  i.  5. 

Catarrh  from  cold  skin,  xxxv.  1.  3.  xxxv.  2.  3. 

- - - - from  thin  caps  in  sleep,  xviii.  15. 

Catenation  of  motions  defined,  ii  it.  iv.  7. 

------  cause  of  them,  xvii.  1.3. 

------  described,  xvii. 

- - - - - - continue  sometime  after  their  production,  xvii.  1.  3. 

voluntary  onesdissevered  in  sleep,  xvii.  1. 12.  xvii.  3. 13. 

Cathartics,  external,  their  operation,  xxix.  7.  6. 

Causation,  animal,  defined,  ii.  11.  iv.  7. 

Cause  of  causes,  xxxix.  4.  8. 

Causes  inert  and  efficient,  xxxix.  8.  2. 

- - - adtive  and  passive,  xxxix.  8.  3. 

- - - proximate  and  remote,  xxxix.  8.  4. 

Chick  in  the  egg,  oxygenation  of,  xxxviii.  2. 

Child  riding  on  a stick,  xxxiv.  2.  6. 

Chilness  after  meals,  xxi.  3.  xxxv.  1.  1. 

Cholera,  case  of,  xxv.  13. 

Circulation  in  the  eye  visible,  xl.  10.  4. 

Cold  in  the  head,  xii.  7.  5. 

: perceived  by  the  teeth,  xxxii.  3.1.  xiv.  6. 

' air,  uses  of  in  fevers,  xxxii.  3.  2. 

feet,  produces  coryza,  xxxv.  2.  3.  xxxv.  1.  3.  f 

bath,  why  it  strengthens,  xxxii.  3.  3. 

short  and  cold  breathing  in  it,  xxxii.  3.  2. 

- - - produces  a fever-fit,  xxxii.  3.  2. 

- - - fit  of  fever  the  consequence  of  hot  fit,  xxxii.  9.  3, 

bathing  in  pulmonary  hemorrhage,  xxvii.  1. 

- - - fits  of  fever,  xxxii.  4.  xxxii,  9.  xvii.  3.  3. 

Comparing  ideas,  xv.  3. 

Consciousness,  xv.  3.  4.  ■ 

Consciousness  in  dreams,  xviii.  13. 

Consumption,  its  temparament,  xxxi.  1.  and  2. 

- - of  dark  eyed  patients,  xxvii.  2. 

-...-.-of  light-eyed  patients,  xxviii;  2. 

-.--..-is  contagious,  xxxiii.  2.  7. 

Consent  of  parts.  See  Sympathy. 

Contagion,  xii.  3.  6.  xix.  9.  xxxiii.  2.  6.  and  8.  xxxii.  3.  3, 
------  does  not  enter  the  blood,  xxxiii.  2.  10.  xxii.  3.  3. 

Contraction  and  attradfion,  iv.  1. 

. - - - . - of  fibres  produces  sensation,  iv.  5.  xii.  1.  6. 
------  continues  some  time,  xii.  1.  5. 

------  alternates  with  relaxation,  xii.  1.  3. 

Convulsion,  xvii.  1.  8.  xxxiv.  1.  1.  and  4.  iii.  5.  8, 

of  particular  muscles,  xvii.  1.  8. 

------  periods  of,  xxxvi.  3.  9. 

Kk  k 


Colours 


index:. 


42i 

Colours  of  animals,  efficient  cause  of,  xxxix.  5. 

....  of  eggs  from  female  imagination,  xxxix.  5. 

- - - - of  the  choroid  coat  of  the  eye,  xxxix.  5. 

- - - - of  birds  nests,  xvi.  13. 

Coryza.  See  Catarrh. 

Cough,  nervous,  periods  of,  xxxvi.  3.  9. 

Cramp,  xviii.  15.  xxiv.  1.  7. 

Critical  days  from  lunations,  xxxvi.  4. 

D 

Darkish  room,  why  we  see  well  in  it,  xii.  2.  1. 

Debility  sensorial  and  stimulatory,  xii.  2.  1. 

- - - - direft  and  indiredt  of  Dr.  Brown,  xii.  2.  r.  xxxii.  3.  ♦. 
...  . See  Weakness. 

- - - - from  drinking  spirits,  cure  of,  xii.  7.  8. 

-----  in  fevers,  cure  of,  xii.  7.  8. 

Deliberation,  what,  xxxiv.  1. 

Desire,  origin  of,  xi.  2.  3. 

Diabetes  explained,  xxix.  4. 

- - - - with  bloody  urine,  xxvii.  2. 

Diarrhoea,  xxix.  4. 

Digestion,  xxxiii.  1.  xxxvii. 

-----  strengthened  by  emetics,  xxxv.  1.  3. 

- - - - - strengthened  by  regular  hours,  why,  xxxvi.  2.1. 
Digitalis,  use  of  in  dropsy,  xxix.  5.  2. 

Dilirium,  two  kinds  of,  xxxiii.  1.4.  xxxiv.  2.  2. 

-----  cases  of,  iii.  5.  8. 

-----  prevented  by  dreams,  xviii.  2. 

Distention  a<fts  as  a stimulus,  xxxii.  4. 

-----  See  Extension. 

Distinguishing,  xv.  3. 

Diurnal  circle  of  adtions,  xxv.  4. 

Doubting,  xv.  3. 

Dreams,  viii.  1.2.  xiv.  2.  5. 

- - - - their  inconsistency,  xviii.  16. 

- - - - no  surprise  in  them,  xviii.  17. 

- - - - much  novelty  of  combination,  xviii.  9. 

Dropsies  explained,  xxix.  5.  1. 

Dropsy  cured  by  insanity,  xxxiv.  2.  7. 

- - - -cureof,  xxix.  5.  2. 

Drunkenness.  See  Intoxication,  xxi. 

-------  diminished  by  attention,  xxi.  8. 

Drunkards  weak  till  next  day,  xvii.  1.  7. 

-----  stammer,  and  stagger,  and  weep,  xii.  4.  1.  xxi.  4. 

see  objects  double,  why,  xxi.  7. 

become  delirious,  sleepy,  stupid,  xxi.  5. 

Dyspnoea  in  cold  both,  xxxii.  3.  2. 


Ear, 


I N D E X. 


4“5 


E 

Ear,  a good  one,  xvi.  10, 

- - - noise  in,  xx.  7. 

Eggs  of  frogs,  fish,  fowl,  xxxix.  2. 

of  birds,  why  spotted,  xxxix.  £. 

with  double  yolk,  xxxix.  4.  4. 

Electricity,  xii.  1.  xiv.  9. 

- - — - - jaundice  cured  by  it,  xxx.  2. 

Embryon  produced  by  the  male,  xxxix.  2. 

-----  consists  of  a living  fibre,  xxxix.  4. 

absorbs  nutriment,  receives  oxygen,  xxxix.  1. 

-----  its  aftions  and  sensations,  xvi.  '2. 

Emetic.  See  Vomiting. 

Emotions,  xi.  2.  2. 

Ennui,  or  tedium  vite,  xxxjv.  2.  3.  xxxiii.  1.  1.  xxxix.  6.  ,Clg6S 
ii.  1. 1. 

Epileptic  fits  explained,  xxxiv.  1.4.  xxvii.  2. 

------  in  sleep,  why,  xviii.  14.  and  15. 

Equinoxial  lunations,  xxxii.  6. 

Excitability  perpetually  varies,  xii.  1.  7. 

- synonymous  to  quantity  of  sensorial  power,  xii.  x.  7, 

Exercise,  its  use,  xxxii.  3.  3. 

Exertion  of  sensorial  power  defined,  xii.  2.  1. 

Existence  in  space,  xiv.  2.  3. 

Extension,  sense  of,  xiv.  7. 

Eyes  become  black  in  some  epilepsies,  xxvii.  2. 

F 

Face,  flushing  of  after  dinner,  xxxv.  1.  1. 

- - - why  first  affeCted  in  small-pox,  xxxv.  1,1. 

- - - red  from  inflamed  liver,  xxxv.  2.  2. 

Fainting  fits,  xii.  5.  1.  xiv.  7. 

Fear,  language  of,  xvi.  8.  1. 

- - - a cause  of  fever,  xxxii.  S. 

- - - cause  of,  xvii.  3.  7. 

Fetus.  See  Embryon,  xvi.  2.  xxxix.  r. 

Fevers,  irritative,  xxxii.  1,. 

- - - - intermittent,  xxxii.  1.  xxxii.  3. 

- - - - sensitive,  xxxiii.  1. 

- - - - not  an  effort  of  nature  .for  relief,  xxxii.  10. 

- - - - paroxysms  of,  xii.  7.  1.  xii.  2.  3.  xii.  3.  5. 

- - - - why  some  intermit  and  not  others,  xxxvi.  1, 

- - - - cold  fits  of,  xxxii.  4.  xxxii.  9.  xvii.  3.  3. 

- - - - periods  of,  xxxvi.  3. 

- - - - have  solar  or  lunar  periods,  xxxii.  6. 

- - - - source  of  the  symptoms  of,  xxxii.  x. 

- - - - prostration  of  strength  in,  xii.  4.1.  xxxii.  3.2. 

- - - - cure  of,  xii.  6.  1, 

Fevers, 


INDEX. 


424 

Fevers,  how  cured  by  the  bark,  xii.  3.  4. 

- - - - cured  by  increased  volition,  xii.  2..  4.  xxxiv.  2.  8. 

- - - - best  quantity  of  stimulus  in,  xii.  7.  8. 

Fibres.  See  Muscles. 

- - - - their  mobility,  xii.  1.  7.  xii.  1.  1. 

- - - - contractions  of,  vi.  xii.  1.  1. 

- - - - four  classes  of  their  motions,  vi. 

- - - - their  motions  distinguished  from  sensorial  ones,  v.  5. 
Figure,  xiv.  2.  2.  iii.  1. 

Fish,  their  knowledge,  xvi.  14. 

Foxglove,  its  use  in  dropsies,  xxix.  5.  2. 

-----  overdose  of,  xxv.  1 7. 

Free-will,  xv.  3.  7. 

G 

Gall-stone,  xxv.  17.  See  Bile-stones. 

Generation,  xxxiii.  1.  xxxix. 

Gills  of  fish,  xxxviii.  2. 

Glands,  xxii.  1.  conglobate  glands,  xxii.  2. 

- - - - have  their  peculiar  stimulus,  xi.  1. 

- - - - their  senses,  xiv.  9.  xxxix.  6. 

- - - - invert  their  motions,  xxv.  7. 

- - - - increase  their  motions,  xxv.  7. 

Golden  rule  for  exhibiting  wine,  xii.  7.  8. 

------  for  leaving  otf  wine,  xii.  7.  8- 

Gout  from  inflamed  liver,  xxxv.  2.  2.  xviii.  15.  xxiv.  2.  S. 

- - - in  the  stomach,  xxi.  2.  8.  xxv.  17. 

- - - why  it  returns  after  evacuations,  xxxii.  4. 

- - - owing  to  vinous  spirit  only,  xxi.  10. 

- - - periods  of,  xxxvi.  3.  6. 

Grinning  in  pain,  xxxiv.  1.  3. 

Gyration  on  one  foot,  xx.  5.  and  6. 

H 

Habit  defined,  ii.  11,  iv.  7. 

Haemorrhages,  periods  of,  xxxvi.  3.  10. 

-  from  paralysis  of  veins,  xxvii.  1.  and  2. 

Harmony,  xxii.  2. 

Head-achs,  xxxv.  2.  1. 

Hearing,  xiv.  4. 

Heat,  sense  of,  xiv.  6.  xxxii.  3.  1. 

- - - produced  by  the  glands,  xxii.  3. 

- - - external  and  internal,  xxxii.  3.  1. 

- - - atmosphere  of  heat,  xxxii.  3.  1. 

- - - increases  during  sleep,  xviii.  15. 

Hemicrania,  xxxv.  2.  1.  . 

Hemicrania  from  decaying  teeth,  xxxv.  2.  1. 

Hepatitis,  cause  of,  xxxv.  2.  3. 

Hereditary  diseases,  xxxix.  7.  6. 

• Hermaphrodite 


INDEX. 


4-S 

Hermaphrodite  inseCts,  xxxix.  5. 

Herpes,  xxviii.  2. 

- - - - from  inflamed  kidney,  xxxv.  2.  2. 

Hunger,  sense  of,  xiv.  8. 

Hydrophobia,  xxii.  3.  3. 

Hypochondriacism,  xxxiii.  1.  1.  xxxiv.  2.  3. 

I 

Ideas  defined,  ii.  7. 

- - - are  motions  of  the  organs  of  sense,  iii.  4.  xviii.  5.  xviii. 
10.  xviii.  6. 

- - - analogous  to  muscular  motions,  iii.  5. 

- - - continue  some  time;  xx.  6. 

- - - new  ones  cannot  be  invented,  iii.  6.  1. 

- - - abstracted  ones,  iii.  7.  4. 

- - - inconsistent  trains  of,  xviii.  16. 

- - - perish  with  the  organ  of  sense,  iii.  4.  4. 

- - - painfui  from  inflammation  of  the  organ,  iii.  5.  5. 

- - - irritative  ones,  vii.  1.  4.  vii.  3.  2.  xv.  2.  xx.  7. 

- - - of  resemblance,  contiguity,  causation,  viii.  3.  2.  x.  3.  3. 

- - - resemble  the  figure  and  other  properties  of  bodies,  xiv.  2.  2. 

- - - received  in  tribes,  xv.  1. 

- - - of  the  same  sense  easier  combined,  xv.  1 . 1 . 

- - - of  reflection,  xv.  1.  6.  ii.  12. 

Ideal  presence,  xv.  1.7. 

Identity,  xv.  3.  5.  xviii.  13. 

Iliac  passion,  xxv.  15. 

Imagination,  viii.  1.  2.  xv.  1.  7.  xv.  2.  2. 

of  the  male  forms  the  sex,  xxxix.  6. 

Immaterial  beings,  xiv.  1.  xiv.  2.  4. 

Imitation,  origin  of,  xii.  3.  3.  xxxix.  5.  xxii.  3.  xvi.  7. 
Impediment  of  speech,  xvii.  1.  10.  xvii.  2.  10. 

Infeftion.  See  Contagion. 

Inflammation,  xii.  2.  3.  xxxiii.  2.  2. 

-  - great  vascular  exertion  in,  xii.  2.  1. 

-------  not  from  pains  from  defeft  of  stimulus,  xxxiii.  2.  3. 

-------  of  parts  previously  insensible,  xii.  3.  7. 

.......  often  distant  from  its  cause,  xxiv.  8. 

.......  observes  solar  days,  xxxii.  6. 

of  the  eye,  xxxiii.  3.  1. 

of  the  bowels  prevented  by  their  continual  aCfion  in 
sleep,  xviii.  2. 

Inoculation  with  blood,  xxxiii.  2.  10. 

Insane  people,  their  great  strength,  xii.  1. 

Insanity  (see  Madness)  pleasureable  one,  xxxiv.  2.  6. 

InseCts,  their  knowledge,  xvi.  15.  and  16. 

- - - - in  the  heads  of  calves,  xxxix.  1. 

- - - - class  of,  xxxix.  4* 

InstinCtive  aCtions  defined,  xvi.  1. 


Intestines 


INDEX. 


4^6 

Intestines,  xxv.  3. 

Intoxication  relieves  pain,  why,  xxi.  3. 

------  from  food  after  fatigue,  xxi.  2. 

------  diseases  from  it,  xxi.  10. 

------  See  Drunkenness. 

Intuitive  analogy,  xvii.  3.  7. 

Invention,  xv.  3.  3. 

Irritability  increases  during  sleep,  xviii.  15. 

Itching,  xiv.  9. 

J 

Jaw -locked,  xxxiv.  1.5. 

Jaundice  from  paralysis  of  the  liver,  xxx.  2. 

. . - - cured  by  electricity,  xxx.  2. 

Judgment,  xv.  3. 

K 

Knowledge  of  various  animals,  xvi.  n. 

L 

Lacrymal  sack,  xvi.  8.  xxiv.  2.  and  7. 

Lafteals,  paralysis  of,  Xxviii.  See  Absorbents. 

Lady  playing  on  the  harpsichord,  xvii.  2. 

- - - distressed  for  her  dying  bird,  xvii.  2.  10. 

Language,  natural,  its  origin,  xvi.  7.  and  8. 

- . . . . of  various  passions  described,  xvi.  8. 

-----  artificial,  of  various  animals,  xvi.  9. 

-----  theory  of,  xxxix.  8.  3. 

Lapping  of  puppies,  xvi.  4. 

Laughter  explained,  xxxiv.  r.  4. 

- - - - - from  tickling,  xvii.  3.  3.  xxxiv.  1.4. 

- - - - from  frivolous  ideas,  xxxiv.  1.4.  xviii.  is. 

Life,  long,  art  of  producing,  xxxvii. 

Light  has  no  momentum,  iii.  3.  1. 

Liquor amnii,  xvi.  xxxviii.  2. 

.-  - - is  nutritious,  xxxviii.  3. 

- - - frozen,  xxxviii.  3. 

Liver,  paralysis  of,  xxx.  1.4. 

- - - large  of  geese,  xxx.  1 . 6. 

Love,  sentimental,  its  origin,  xvi.  6. 

- - - animal,  xiv.  8.  xvi.  3. 

Lunar  periods  affedt  diseases,  xxxii.  6. 

Lust,  xiv.  8.  xvi.  3. 

Lymphatics,  paralysis  of,  xxviii.  See  Absorbents. 

M 

Msd-dog,  bite  of,  xxii.  5.  3. 

Madness,  xxxiv.  2.  1.  xii.  2.  1. 

Magnetism,  xii.  1.  1. 

Magnifying 


INDEX. 


427 


Magnifying  objects,  new  way  of,  xl.  10.  5. 

Male  animals  have  teats,  xxxix.  4.  8. 

- - . pigeons  give  milk,  xxxix.  4.  8. 

Man  distinguished  from  brutes,  xi.  2.  3.  xvi.  17, 

Material  world,  xiv.  1.  xiv.  3.  5.  xviii.  7. 

Matter,  penetrability  of,  xiv.  2.  3. 

- - - - purulent,  xxxiii.  2.4. 

Measles,  xxxiii.  2.  9. 

Membranes,  xxvi.  2. 

Memory  defined,  ii.  10.  xv.  z.  7.  xv.  3. 

Menstruation  by  lunar  periods,  xxxii.  6. 

Miscarriage  from  fear,  xxxix.  5. 

Mobility  of  fibres,  xii.  1.  7. 

Momentum  of  the  blood,  xxxii.  5.  2. 

sometimes  increased  by  venesedtion,  xxxii.  5.  4. 

Monsters,  xxxix.  4. 4.  and  5.2. 

- - - - - without  heads,  xxxviii.  3. 

Moon  and  sun,  their  influence,  xxxii.  6. 

Mortification,  xxxiii.  3.  3. 

Motion  is  either  cause  or  effedt,  i.  xiv.  2.  2. 

~ - - - primary  and  secondary,  i. 

- - - - animal,  i.  iii.  1. 

- - - - propensity  to,  xxii.  1. 

- - - - animal,  continue  sometimeaftertheirprodudlion,  xvii.  1.3. 

- - - - defined  a variation  of  figure,  iii.  1.  xiv.  2.  2.  xxxzX.  7. 
Mucus,  experiment  on,  xxvi.  1 . 

- - - - secretion  of,  xxvi.  2. 

Mules,  xxxix.  4.  5,  and  6.  xxxix.  5.  2. 

Mule  plants,  xxxix.  2. 

Muscae  volitantes,  xl.  2. 

Muscles  constitute  an  organ  of  sense,  xiv.  7.  ii.  3. 

- - - - stimulated  by  extension,  xi.  1.  xiv.  7. 

- - - - con tradt  by  spirit  of  animation,  xii.  1.  1.  and  3. 

Music,  xvi.  10.  xxii.  2. 

Musical  time,  why  agreeable,  xii.  3.3. 

N 

Nausea,  xxv.  6. 

Nerves  and  brains,  ii.  2.  3. 

- - - - extremities  of  form  the  whole  system,  xxxvii.  3. 

- - - - are  not  changed  with  age,  xxxvii.  4. 

Nervous  pains  defined,  xxxiv.  1.  1. 

Number  defined,  xiv.  2.  2. 

Nutriment  for  the  embryon,  xxxix.  5.  2. 

Nutrition  owing  to  stimulus,  xxxvii.  3. 

by  animal  selection,  xxxvii.  3. 

when  the  fibres  are  elongated,  xxxvii.  3. 

- - - - - like  inflammation,  xxxvii.  3. 


Objedts 


42.8 


INDEX. 


O 

Objects  long  viewed  become  faint,  iii.  3.  2. 

Ocular  speftra,  x!. 

Oil  externally  in  diabetes,  xx'x-  4. 

Old  age  from  inirritability,  xxxvii.  , 

Opium  is  stimulant,  xxxii.  2.  2. 

- - - - promotes  absorption  alter  evacuation,  xxxiii.  2.  10. 

- - - - in  increasing  doses,  xii.  3.  1. 

Organs  of  sense,  ii.  5.  and  6. 

Organs  when  destroyed  cease  to  produce  ideas,  iii.  4.  4. 

Organic  particles  of  Butfon,  xxxvii.  3.  xxxix.  3.  3. 
Organ-pipes,  xx.  7. 

Oxygenation  of  the  blood,  xxxviii. 

P 

Pain  from  excess  and  defeft  of  motion,  iv.  5.  xii.  5.  3.  xxxiv. 
J.  xxxv.  2.  1. 

- - - not  felt  during  exertion,  xxxiv.  1.  2. 

- - - from  greater  contraction  of  fibres,  xii.  1.  6. 

- - - from  accumulation  of  sensorial  power,  xii.  5.  3.  xxiii.  3.  1. 

- - - from  light,  pressure,,  heat,  caustics,  xiv.  9. 

- - - in  epilepsy,  xxxv.  2.  1 . 

- - - distant  from  its  cause,  xxiv.  8. 

- - - from  stone  in  the  bladder,  xxxv.  2.  x. 

- - - of  head  and  back  from  defeft,  xxxii.  3. 

- - - from  a gall-stone,  xxxv.  2.  1.  xxv.  17. 

- - - of  the  stomach  in  gout,  xxv.  17. 

- - - of  shoulder  in  hepatites,  xxxv.  2.  4. 

- - - produces  volition,  iv.  6. 

Paleness  in  cold  fit,  xxxii.  3.  2. 

Palsies  explained,  xxxiv.  1.  7. 

Paralytic  limbs  stretch  from  irritation,  vii.  1.  3. 

- - - - - patients  move  their  sound  limb  much,  xii.  5.  1. 
Paralysis  from  great  exertion,  xii.  4.  6. 

from  less  exertion,  xii.  5.  6. 

of  the  ladfeals,  xxviii. 

of  the  liver,  xxx.  4. 

of  the  right  arm,  why,  xxxiv.  1.  7. 

of  the  veins,  xxvii.  2. 

Particles  of  matter  w iii  not  approach,  xii.  1.  1. 

Passions,  xi.  2.  2. 

- - - - connate,  xvi.  1. 

Pecking  of  chickens,  xvi.  4. 

Perception  defined,  ii.  8.  xv.  3.  1. 

Periods  of  agues,  how  formed,  xxxii.  3.  4. 

- - - - of  diseases,  xxxvi. 

- - - - of  natural  adt ions  and  of  diseased  actions,  xxxvi. 
Perspiration  in  fever-fits,  xxxii.  9.  See  Swear. 


Petechia:. 


INDEX, 


A29 

iPetechise,  xxvii.  2. 

Pigeons  secrete  milk  in  their  stomachs,  xxxix.  4.  8. 

Piles,  xxvii.  2. 

Placenta  a pulmonary  organ,  xxxviii.  2. 

Pleasure  of  life  xxxiii.  1.  xxxix.  5. 

- - - - from  greater  fibrous  contractions,  xii.  1.  6, 

- - - - what  kind  causes  laughter,  xxxiv.  1.  4. 

- - - - what  kind  causes  sleep,  xxxiv.  1.  4. 

Pleurisy,  periods  of,  xxxvi.  3.  7. 

cause  of,  xxxv.  2.  3. 

Prometheus,  story  of,  xxx.  3. 

Prostration  of  strength  in  fevers,  xii.  4.  1. 

Pupils  of  the  eyes  large,  xxxi.  1. 

Puise  quick  in  fevers  with  debility,  xii.  1.  4.  xii.  5.  4.  xxxii.  2.  if 

- - - in  fevers  with  strength,  xxxii.  2. 

- - - from  defect  of  blood,  xxxii.  2.  3.  xii.  1.4. 

- - - weak  from  emetics,  xxv.  1 7. 

Q 

Quack  advertisements  injurious.  Apology. 

Quadrupeds  have  no  sanguiferous  lochia,  xxxviii.  2. 

------  have  nothing  similar  to  the  yolk  of  eggs,  xxxix.  it, 

R 

Rhap’nania,  periods  of,  xxxvi.  3.  9. 

Reason,  ix.  1.  2.  xv.  3. 

Reasoning,  xv.  3. 

RecolleCfion,  ii.  10.  ix.  1.2.  xv.  2.  3. 

Relaxation  and  bracing,  xxxii,  3.  2. 

Repetition,  why  agreeable,  xii.  3.  3.  xii.  2. 

Respiration  affeCted  by  attention,  xxxvi.  2.  1. 

Restlessness  in  fevers,  xxxiv.  1.  2. 

Retrograde  motions,  xii.  3.  3.  xxv.  6.  xxix.  jr. 

------  of  the  stomach,  xxv.  6. 

------  of  the  skin,  xxv.  3. 

i -----  of  fluids,  how  distinguished,  xxix.  8. 

x . - - _ . how  caused,  xxix.  11.  3. 

*■ diseases,  synopsis  of,  xxix.  9. 

Retina  is  fibrous,  iii.  2.  xl.  1. 

- - - - is  aCtive  in  vision,  iii.  3.  xl.  1. 

- - - - excited  into  spasmodic  motions,  xl.  7. 

- - - - is  sensible  during  sleep,  xviii.  3.  xix.  8. 

Reverie,  xix.  1.  xxxiv.  3. 

■t----  case  of  a sleep-walker,  xix.  2. 

- - - - - is  an  epileptic  disease,  xix.  2. 

Rocking  young  children,  xxi.  4. 

Rot  in  sheep,  xxxii.  7. 

Ruminating  animals,  xxv.  1. 

Rhymes  in  poetry,  why  agreeable,  xxii.  2- 

LU 


Saliva 


43® 


r n d e r. 


s 

Saliva  produced  by  mercury,  xxiii. 

by  food,  xxiii.  i. 

by  ideas,  xxiii.  2.  and  5. 

by  disordered  volition,  xxiii.  7. 

Schirrous  tumours  revive,  xii.  2.  2. 

Screaming  in  pain,  xxxiv.  1.  2. 

Scrophula,  its  temperament,  xxxi.  1. 

------  xxviii.  2.  xxxix.  4.  5. 

Scurvy  of  the  lungs,  xxvii.  2. 

Sea-sickness,  xx.  4. 

-------  stopped  by  attention,  xx.  5. 

Secretion,  xxxiii.  1.  xxxvii. 

-----  increased  during  sleep,  xviii.  16. 

Seeds  require  oxygenation,  xxxviii.  2. 

Sensation  defined,  ii.  9.  v.  2.  xxxix.  8.  4. 

-----  diseases  of,  xxxiii. 

-----  from  fibrous  contradfions,  iv.  5.  xii.  1.  6. 

in  an  amputated  limb,  iii  7.  3. 

-----  affedfs  the  whole  sensorium,  xi.  2. 

-----  produces  volition,  iv.  6. 

Sensibility  increases  during  sleep,  xviii.  15. 

Sensitive  motions,  viii.  xxxiii.  2.  xxxiv  1. 

-----  fever  of  two  kinds,  xxxiii.  1.  2. 

-----  ideas,  xv.  2.  2. 

Sensorium  defined,  ii.  1. 

Senses  corredt  one  another,  xviii.  7. 

-<  distinguished  from  appetites,  xxxiv.  1.  1. 

Sensorial  power.  See  Spirit  of  Animation. 

-----  great  expence  in  the  vital  motions,  xxxii.  3.  2. 
-----  two  kinds  of  exerted  in  sensitive  fevers,  xxxiii.  1.  3. 
-----  powers  defined,  v.  1. 

-----  motions  distinguished  from  fibrous  motions,  v.  3. 
-----  not  much  accumulated  in  sleep,  xviii.  2. 

-----  powers,  accumulation  of,  xii.  5.  1. 

-----  exhaustion  of,  xii.  4.  1 . 

wasted  below  natural  in  hot  fits,  xxxii.  9.  3. 

-----  less  exertion  of  produces  pain,  xii.  5.  3. 

-----  less  quantity  of  it,  xii.  5.4. 

Sensual  motions  distinguished  from  muscular,  ii.  7. 

Sex  owing  to  the  imagination  of  the  father,  xxxiv.  5. 

xxxix.  7.  6.  xxxix.  6.  2.  xxxix.  6.  7. 

Shingles  from  inflamed  kidney,  xxxv.  2.  2. 

Shoulders  broad,  xxxi.  1.  xxxix.  7.  6. 

Shuddering  from  cold,  xxxiv.  1.  1.  and  2. 

Sight,  its  accuracy  in  men,  xvi.  6. 

- Skin,  skurf  on  it,  xxvi.  1. 

Sleep  suspends  volition,  xvii.  1. 

" Sleep 


1 N D E X. 


43* 

;Sleep  defined,  xviii.  21. 

- - - remote  causes,  xviii.  20. 

- - - sensation  continues  in  it,  xvii.  2. 

- - - from  food,  xxi.  1. 

- - - from  rocking,  uniform  sounds,  xxi.  1. 

- - - from  wine  and  opium,  xxi.  3. 

- - - why  it  invigorates,  xii.  5.  1. 

- - - pulse  slower  and  fuller,  xxxii.  2.  2. 

- - - interrupted,  xxvii.  2. 

- - - from  breathing  less  oxygene,  xviii.  20. 

- - - from  being  whirled  on  a millstone,  xviii.  20. 

- - - from  application  of  cold,  xviii.  20. 

Sleeping  animals,  xii.  2.  2. 

Sleep-walkers.  See  Reverie,  xix.  1. 

Small-pox,  xxxiii.  .2.  6.  xxxix.  6.  1. 

eruption  first  on  the  face,  why,  xxxv.  1.  1.  xxxiii. 

2.  10. 

the  blood  will  not  infedl,  xxxiii.  2.  10. 

------  obeys  lunations,  -xxxvi.  4. 

Smell,  xiv.  3.  xvi.  3. 

Smiling,  origin  of,  xvi.  S.  4. 

Solidity,  xiv.,2.  4. 

Somnambuiation.  See  Reverie,  xix,  1. 

Space,  xiv.  2.  2. 

Spasm,  dodtrine  of,  xxxii.  xq. 

Spedtra,  ocular,  xi. 

- - - - mistaken  for  spedtres,  xl.  2. 

- - — vary  from  long  inspedlion,  iii.  3.  5. 

Spirit  of  animation.  See  Sensorial  power. 

- - of  animation  causes  fibrous  contradfion,  iv.  2.  ii.  1.  xiv. 
2-  4- 

- - - possesses  solidity,  figure,  and  other  properties  of  matter, 
xiv.  2.  3. 

Spirits  and  angels,  xiv.  2.  4. 

Stammering  explained,  xvii.  1.  10.  xvii.  2.  10. 

Stimulus  defined,  ii.  13.  iv.  4.  xii.  2.  1. 

-----  of  various  kinds,  xi.  1. 

-----  with  lessened  effedl,  xii.  3.1. 

with  greater  effedl,  xii.  3.3. 

-----  ceases  to  produce  sensation,  xii.  3.  3. 

Stomach  and  intestines,  xxv. 

-----  inverted  by  great  stimulus,  xxv.  6. 

-----  its  adlions  decreased  in  vomiting,  xxxv.  1.  3. 

a blow  on  it  occasions  death,  xxv.  ly. 

Stools  black,  xxvii.  2. 

Strangury,  xxxv.  2.  1. 

Sucking  before  nativity,  xvi.  4. 

Suckling  children,  sense  of,  xiv.  8. 

Suggestion,  defined,  ii.  io.  xv.  2.  4, 


Sun 


INDEX 


43a 

Sun  and  moon,  their  influence,  xxxii.  6. 

Surprise,  xvii.  3.  7.  xviii.  17. 

Suspicion  attends  madness,  xxxiv.  2. 

Swallowing,  aft  of,  xxv.  1.  xvi.  4. 

Sweat,  cold,  xxv.  9.  xxix.  6. 

- - - in  hot  fit  of  fever,  xxxii.  9. 

- - - - in  a morning,  why,  xviii.  13. 

Sweaty  hands  cured  by  lime,  xxix.  4.  9. 

Swinging  and  rocking,  why  agreeable,  xxi.  3. 

•Sympathy,  xxxv.  1. 

Syncope,  xii.  7.  1.  xxiv.  1.  6. 

T 

Tape-worm,  xxxix.  2. 

Taste,  sense  of,  xiv.  3. 

Tears,  secretion  of,  xxiv. 

- - - from  grief,  xvi.  8.  2. 

- - - from  tender  pleasure,  xvi.  S.  3. 

- - - from  stimulus  of  nasal  duft,  xvi.  8.  xxiv.  4. 

- - - by  volition,  xxiv.  6. 

T eeth  decaying  cause  headachs,  xxxv.  2.  1. 

Temperaments,  xxxi. 

Theory  of  medicine,  wanted.  Apology. 

Thirst,  sense  of,  xiv.  8. 

- - - - why  in  dropsies,  xxix.  5. 

Tickle  themselves,  children  cannot,  xvii.  3.  5. 

Tickling,  xiv.  9. 

Time,  xiv.  2.  2.  xvii.  12. 

- - - lapse  of,  xv.  3.  6. 

- - - poetic  and  musical,  why  agreeable,  xxii.  2. 

- - - dramatic,  xviii.  12. 

Tasdium  vitae.  See  Ennui. 

Tooth-edge,  xvi.  10.  iii.  4.  3.  xii.  3.  3. 

Touch,  sense  of,  xiv.  2.  1. 

- - - - liable  to  vertigo,  xxi.  9. 

- - - - of  various  animals,  xvi.  6. 

Trains  of  motions  inverted,  xii.  3.  5. 

Transfusion  of  blood  in  nervous  fever,  xxxii.  4. 

Translations  of  matter,  xxix;  7. 

Typhus,  best  quantity  of  stimulus  in,  xii.  7.  8. 

- - - - periods  of  observe  lunar  days,  xxxii.  6. 

U 

Ulcers,  art  of  healing,  xxxiii.  3.  s 

- - - - of  the  lungs,  why  difficult  to  heal,  xxviii.  2 
Uniformity  in  the  fine  arts,  why  agreeable,  xxii.  2. 

Urine  pale  in  intoxication,  xxi.  6. 

- - - paucity  of  in  anasarca,  why,  xxix.  5. 

; its  passage  from  intestines  to  bladder,  xxix.  3. 

- v - copious  during  sleep,  xviii.  13, 

Variation, 


INDEX. 


433 


V 

Variation,  perpetual,  of  irritability,  xii.  2.  1, 

Vegetable  buds  are  inferior  animals,  xiii.  1 . 

-----  exactly  resemble  their  parents,  xxxix. 
-----  possess  sensation  and  volition,  xiii.  2. 

- have  associate  and  retrograde  motions,  xiii.  4. 

- - their  anthers  and  stigmas  are  alive,  xiii.  5. 

- - - - - have  organs  of  sense  and  ideas,  xiii.  5. 

- - - - - contend  for  light  and  air,  xxxix.  4.  8. 

duplicature  of  their  flowers,  xxxix.  4.  4. 

Veins  are  absorbents,  xxvii.  1. 

- - - paralysis  of,  xxvii.  1 . 

Venereal  orgasm  of  brutes,  xxxii.  6. 

Venesedtion  in  nervous  pains,  xxxii.  5.  4. 

Verbs  of  three  kinds,  xv.  3.  4. 

Verses,  their  measure,  xxii.  2. 

Vertigo,  xx.  defined,  xx.  11. 

- - - - in  looking  from  a tower,  xx.  1 . 

in  a ship  at  sea,  xx.  4. 

- - - - of  all  tne  senses,  xxi.  9. 

- - - - by  intoxication,  xxxv.  1.2. 

Vibratory  motions  perceived  after  sailing,  xx.  5.  xx.  10. 
Vis  medicatrix  of  nature,  xxxix.  4.  7. 

Vision,  sense  of,  xiv.  3. 

Volition  defined,  v.  2.  xxxiv.  r. 

- - - - affects  tne  whole  sensorium,  xi.  2. 

- - - - diseases  of,  xxxiv. 

Voluntarily,  x.  2. 4. 

Voluntary  motions,  ix.  xxxiv.  r. 

- - — — t ideas,  xv.  2.  3. 

- - - - - criterion  of,  xi.  2.  3.  xxxiv.  1. 

Vomiting  from  vertigo,  xx.  8. 

- - - - - from-drunkenness,  xx.  8.  xxi.  6. 

by  intervals,  xxv.  8. 

_ - by  voluntary  efforts,  xxv.  6. 

- - - - - of  two  kinds,  xxxv.  1.  3. 

- - - - - in  cold  fit  of  fever,  xxxii.  9.  1. 

- - - - - stopped  by  quicksilver,  xxv.  16. 

....  - weakens  the  pulse,  xxv.,  1 7. 

W 

Waking,  how,  xviii.  14. 

Walking,  how  learnt,  xvi.  3. 

Warmth  in  sleep,  why,  xviii.  15. 

Weakness  defined,  xii.  1.  3.  xii.  2.  1.  xxxii.  3. 
-----  cure  of,  xii.  7.  8.  See  Debility. 

Wit  producing  laughter,  xxxiv.  1.  4. 

World  generated,  xxxix.  4.  8. 

Worm-fluke,  xxxii.  7. 


xxix.  9. 


PLATES. 


1.  The  Plate  confifting  of  one  red  fpot,  at  Se£L  III.  x. 

2.  Confifting  of  one  black  fpot,  at  Sedfi  III.  3.  3. 

3.  Confifting  of  five  concentric  coloured  circles,  at  Sect 

III.  3,  4 - 

4.  Confifting  of  one  yellow  circle  furrounded  by  one  blue 

one,  at  Se6L  XL.  4.  2. 

c. Confifting  of  one  veliow  circle  and  two  blue  ones,  at 

Se4.  XL.  10.  3. 

6. Confifting  of  the  word  BANKS  in  blue  on  a yellow 

ground,  at  Sea.  XL.  10.  5. 


ADVERTISEMENT, 


When  Propofals  were  firft  offered  for  printing  Doaos 
Darwin’s  Zoonomia,  it  was  the  intention  of  the  Pub- 
lifhers  to  have  entered  upon  the  work  immediately — But,  from 
a deficiency  of  fubferiptions,  and  fome  other  caufes,  it  could 
not  then  be  commenced;  and  the  publication  of  it  has  been 
neceffarily  delayed  until  this  time. — As  the  fecond  volume  of 
the  Zoonomia  has  recently  been  publifned  in  England,  and 
as  thofe  who  have  fubferibed  for  this  would  unqueftionably 
wifh  to  poffefs  that  alfo,  the  Publishers  beg  leave  to  inform 
the  Public  that  they  have  determined  to  put  the  fecond  volume 
to  prefs  immediately  upon  its  arrival  in  this  country,  and  that 
they  will  receive  fubferiptions  for  it — to  be  printed  in  uni- 
formity with  the  firft,  and  to  correfpond  in  binding.  A lift 
of  the  names  of  thofe  gentlemen  who  may  favour  the  Pub- 
lifhers  with  their  fubferiptions  fhall  be  inferted  at  the  end  of 
the  work. — Subfcribers  will  receive  their  books  20  per  cent 
cheaper  than  non-fubferibers. 

Neiv-York,  Oflobcr  1,  1796. 


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